PRMT1 promotes H2O2 induced cardiomyocytes cell via mediating arginine methylation of P53.

Long non-coding RNA (lncRNA) plays a pivotal role in the development of myocardial infarction (MI). The aim of this study was to investigate the effects of lncRNA actin filament-associated protein 1 antisense RNA 1 (AFAP1-AS1) on cell cycle, proliferation, and apoptosis. RT-qPCR was used to detect the expression levels of AFAP1-AS1, miR-512-3p, and reticulon 3 (RTN3) in rat model of I/R. The simulated MI environment was constructed. MTT assay and flow cytometry were used to detect changes in cardiomyocyte viability and cell cycle/apoptosis after MI by AFAP1-AS1 silencing or RTN3 silencing. The targeting relationship of miR-512-3p and AFAP1-AS1 and RTN3 in cardiomyocytes was verified by dual luciferase reporter assay. The expression levels of AFAP1-AS1 and RTN3 were significantly upregulated in a rat model of LAD ligation (or MI) ligation, while the expression level of miR-512-3p was significantly reduced. Overexpressed AFAP1-AS1 and RTN3 promoted cardiomyocyte apoptosis and inhibited cardiomyocyte proliferation. MiR-512-3p was a direct target of AFAP1-AS1, and RTN3 was a direct target of miR-512-3p. AFAP1-AS1 promoted the progression of MI by targeting miR-512-3p. AFAP1-AS1 promoted the progression of MI by modulating the miR-512-3p/RTN3 axis. AFAP1-AS1 may be a potential therapy target for MI. Graphical Abstract The role of AFAP1-AS1 in regulating MI injury in vivo. (A) Effect of AFAP1-AS1 in MI injury in vivo. (B) The mRNA level of RTN3 in MI injury in vivo. (C) The protein level of RTN3 in MI injury in vivo. (D) Effect of miR-512-3p in MI model group. (E) TUNEL assay. *P < 0.05, **P < 0.01 vs the sham group; #P< 0.05, ##P < 0.01 vs the MI group.

Infiltration by dendritic cells (DCs) is markedly increased in the infarcted area following myocardial infarction (MI), and DC ablation has been shown to impair angiogenesis in mice post-MI. Exosomes (EXs) have long been known to act as messengers between cells; however, whether EXs derived from DCs can enhance myocardial angiogenesis post-MI remains unknown. The aim of the present study was to elucidate whether EXs derived from DCs induce myocardial angiogenesis via paracrine signaling post-MI. In vitro, suspensions of mouse bone marrow-derived DCs (BMDCs) were incubated with the supernatant of necrotic or normal cultured HL-1 myocardial cells (as the MI or control group, respectively) for 24 h. EXs isolated from the supernatant of BMDCs were termed DEXs, which were added to primary cultures of rat cardiac microvascular endothelial cells (CMECs), and angiogenesis was evaluated by measuring tube formation and vascular endothelial growth factor (VEGF) expression. In vivo, different groups of DEXs were injected into the infarcted myocardium of MI model mice. Then, angiogenesis was evaluated by measuring the number of vessels and the expression of VEGF and CD31 in the infarcted myocardium using immunohistochemistry. Moreover, the expression profile of microRNAs (miRNAs or miRs) in splenic DCs of MI model mice was analyzed by Affymetrix miRNA 4.0 chip assays, then certified in DEXs by reverse transcription-quantitative PCR analysis. Finally, miRNA-loaded DEXs were used to induce tube formation by CMECs and angiogenesis in MI model mice. It was observed that, compared with the control group, DEXs from the MI group significantly upregulated the expression of VEGF in CMECs, enhanced tube formation by CMECs, and upregulated the expression of VEGF and CD31 in the infarcted myocardium of MI model mice. miR-494-3p and miR-16a-5p, which are associated with angiogenesis, were significantly upregulated in splenic DCs of MI model mice by Affymetrix miRNA 4.0 chip assays, miR-494-3p was significantly upregulated and highly enriched in DEXs from the MI group compared with the control, and DEX-miR-494-3p enhanced tube formation by CMECs and angiogenesis in mice post-MI. These results suggest that miR-494-3p may be secreted from DCs via EXs and promotes angiogenesis post-MI. These findings indicate a novel DEX-based approach to the treatment of MI.

Qishen granule (QSG) exerts cardioprotective effects by inhibiting NLRP3 inflammasome and pyroptosis in myocardial infarction rats

Protein arginine methylation is emerging as a significant post-translational modification involved in various cell processes and human diseases. As the major arginine methylation enzyme, protein arginine methyltransferase 1 (PRMT1) strictly generates monomethylarginine and asymmetric dimethylarginine (ADMA), but not symmetric dimethylarginine (SDMA). The two types of dimethylarginines can lead to distinct biological outputs, as highlighted in the PRMT-dependent epigenetic control of transcription. However, it remains unclear how PRMT1 product specificity is regulated. We discovered that a single amino acid mutation (Met-48 to Phe) in the PRMT1 active site enables PRMT1 to generate both ADMA and SDMA. Due to the limited amount of SDMA formed, we carried out quantum mechanical calculations to determine the free energies of activation of ADMA and SDMA synthesis. Our results indicate that the higher energy barrier of SDMA formation (ΔΔG(‡) = 3.2 kcal/mol as compared with ADMA) may explain the small amount of SDMA generated by M48F-PRMT1. Our study reveals unique energetic challenges for SDMA-forming methyltransferases and highlights the exquisite control of product formation by active site residues in the PRMTs.

Tyrosyl-DNA phosphodiesterase (TDP1) hydrolyzes the phosphodiester bond between a DNA 3' end and a tyrosyl moiety and is implicated in the repair of trapped topoisomerase I (Top1)-DNA covalent complexes (Top1cc). Protein arginine methyltransferase 5 (PRMT5) catalyzes arginine methylation of TDP1 at the residues R361 and R586. Here, we establish mechanistic crosstalk between TDP1 arginine methylation and ubiquitylation, which is critical for TDP1 homeostasis and cellular responses to Top1 poisons. We show that R586 methylation promotes TDP1 ubiquitylation, which facilitates ubiquitin/proteasome-dependent TDP1 turnover by impeding the binding of UCHL3 (deubiquitylase enzyme) with TDP1. TDP1-R586 also promotes TDP1-XRCC1 binding and XRCC1 foci formation at Top1cc-damage sites. Intriguingly, R361 methylation enhances the 3'-phosphodiesterase activity of TDP1 in real-time fluorescence-based cleavage assays, and this was rationalized using structural modeling. Together, our findings establish arginine methylation as a co-regulator of TDP1 proteostasis and activity, which modulates the repair of trapped Top1cc.

The aim of this study was to investigate whether microRNA-577 could inhibit myocardial infarction (MI)-induced cardiomyocyte apoptosis by regulating poly ADP-ribose polymerase 1 (PARP1). MI model was successfully established in mice by ligation of the left anterior descending coronary artery (LAD). The expression levels of microRNA-577 and PARP1 in myocardial tissues of mice were examined by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). MI model in cells was established by hypoxia pre-treatment in primary cardiomyocytes and MCM cells. Subsequently, the expression levels of microRNA-577 and PARP1 in hypoxia preconditioning cardiomyocytes were determined as well. Meanwhile, Caspase3 activity in cardiomyocytes overexpressing microRNA-577 or PARP1 was detected using a relative commercial kit. Furthermore, the binding relationship between microRNA-577 and PARP1 was examined by Dual-Luciferase reporter gene assay. Infarct size/risk region and risk region/LV in MI group were (62.1±2.2)% and (57.6±1.9)%, respectively. Both of the above two indexes in the MI group were significantly higher than those of the control group. The serum level of LDH in MI mice increased by 2.8-fold when compared with controls. Meanwhile, the expressions of microRNA-577 and PARP1 in myocardial tissues of MI mice were markedly down-regulated in a time-dependent manner. Compared with normoxia preconditioning cardiomyocytes, microRNA-577 expression in hypoxia preconditioning MCM cells and primary cardiomyocytes was remarkably decreased. Dual-Luciferase reporter gene assay confirmed that microRNA-577 could bind to PARP1. After transfection of microRNA-577 mimics, the expression of PARP1 was significantly down-regulated. Moreover, microRNA-577 over-expression inhibited caspase3 expression in hypoxia preconditioning cells, which could be reversed by PARP1 up-regulation. Similarly, microRNA-577 over-expression markedly decreased infarct size, risk region and serum level of LDH in MI mice, which could be reversed by PAPR1 over-expression. MicroRNA-577 inhibits MI-induced cardiomyocyte apoptosis by degrading PARP1.

Dependence of Doppler echocardiographic transmitral early peak velocity on left ventricular systolic function in coronary artery disease

The protein arginine methyltransferases (PRMTs) are a family of enzymes that catalyze the mono- and dimethylation of arginine residues in a variety of proteins. Although these enzymes play important roles in a variety of cellular processes, aberrant PRMT activity is associated with several disease states, including heart disease and cancer. In an effort to guide the development of inhibitors targeting individual PRMTs, we initiated studies to characterize the molecular mechanisms of PRMT catalysis. Herein, we report studies on the kinetic mechanism of PRMT6. Initial velocity, product inhibition, and dead-end analog inhibition studies with the AcH4-21 and R1 peptides, as well as their monomethylated versions, indicate, in contrast to a previous report, that PRMT6 utilizes a rapid equilibrium random mechanism with dead-end EAP and EBQ complexes.

PKCδ is a key regulator of keratinocyte differentiation that activates p38δ phosphorylation leading to increased differentiation as measured by an increased expression of the structural protein involucrin. Our previous studies suggest that p38δ exists in association with protein partners. A major goal is to identify these partners and understand their role in regulating keratinocyte differentiation. In this study we use affinity purification and mass spectrometry to identify protein arginine methyltransferase 5 (PRMT5) as part of the p38δ signaling complex. PRMT5 is an arginine methyltransferase that symmetrically dimethylates arginine residues on target proteins to alter target protein function. We show that PRMT5 knockdown is associated with increased p38δ phosphorylation, suggesting that PRMT5 impacts the p38δ signaling complex. At a functional level we show that PRMT5 inhibits the PKCδ- or 12-O-tetradecanoylphorbol-13-acetate-dependent increase in human involucrin expression, and PRMT5 dimethylates proteins in the p38δ complex. Moreover, PKCδ expression reduces the PRMT5 level, suggesting that PKCδ activates differentiation in part by reducing PRMT5 level. These studies indicate antagonism between the PKCδ and PRMT5 signaling in control of keratinocyte differentiation.

The aim of this study was to investigate the effects of the GSK-3β/NF-κB pathway on integrin-associated protein (CD47) expression after myocardial infarction (MI) in rats. An MI Sprague Dawley rat model was established by ligating the left anterior descending coronary artery. The rats were divided into three groups: Sham, MI, and SB + MI (SB216763) groups. Immunohistochemistry was used to observe the changes in cardiac morphology. A significant reduction in the sizes of fibrotic scars was observed in the SB + MI group compared to that in the MI group. SB216763 decreased the mRNA and protein expression of CD47 and NF-κB during MI. Primary rat cardiomyocytes (RCMs) and the H9c2 cell line were used to establish in vitro hypoxia models. Quantitative real-time PCR and western blotting analyses were conducted to detect mRNA and protein expression levels of CD47 and NF-κB and apoptosis-related proteins, respectively. Apoptosis of hypoxic cells was assessed using flow cytometry. SB216763 reduced the protein expression of CD47 and NF-κB in RCMs and H9c2 cells under hypoxic conditions for 12 h, and alleviated hypoxia-induced apoptosis. SN50 (an NF-κB inhibitor) also decreased CD47 protein expression in RCMs and H9c2 cells under hypoxic conditions for 12 h and protected cells from apoptosis. GSK-3β upregulates CD47 expression in cardiac tissues after MI by activating NF-κB, which in turn leads to myocardial cell damage and apoptosis.

Protein arginine methyltransferase 6 (PRMT6) is known to catalyze the generation of asymmetric dimethylarginine in polypeptides. Although the cellular role of PRMT6 is not well understood, it has been implicated in human immunodeficiency virus pathogenesis, DNA repair, and transcriptional regulation. PRMT6 is known to methylate histone H3 Arg-2 (H3R2), and this negatively regulates the lysine methylation of H3K4 resulting in gene repression. To identify in a nonbiased manner genes regulated by PRMT6 expression, we performed a microarray analysis on U2OS osteosarcoma cells transfected with control and PRMT6 small interfering RNAs. We identified thrombospondin-1 (TSP-1), a potent natural inhibitor of angiogenesis, as a transcriptional repression target of PRMT6. Moreover, we show that PRMT6-deficient U2OS cells exhibited cell migration defects that were rescued by blocking the secreted TSP-1 with a neutralizing peptide or blocking alpha-TSP-1 antibody. PRMT6 associates with the TSP-1 promoter and regulates the balance of methylation of H3R2 and H3K4, such that in PRMT6-deficient cells H3R2 was hypomethylated and H3K4 was trimethylated at the TSP-1 promoter. Using a TSP-1 promoter reporter gene, we further show that PRMT6 directly regulates the TSP-1 promoter activity. These findings show that TSP-1 is a transcriptional repression target of PRMT6 and suggest that neutralizing the activity of PRMT6 could inhibit tumor progression and therefore may be of cancer therapeutic significance.

Objectives: We aimed to evaluate whether ultrasound (US) and microbubble-mediated delivery of Cluster of Differentiation 151 (CD151) could enhance the therapeutic effects of CD151 on myocardial infarction (MI). Methods: A rabbit model of MI was established by a modified Fujita method. Then, 50 MI rabbits were randomly divided into 5 groups, including G1 (CD151 plasmid and physiological saline in the presence of US); G2 (CD151 and Sonovue in the presence of US); G3 (CD151 and Sonovue in the absence of US); G4 (Sonovue in the absence of US), and a control group (physiological saline in the absence of US). After 14 days of treatment, the expression of CD151 was detected by Western blot. Besides, vessel density of peri-infarcted myocardium was measured by immunohistochemistry, and cardiac function was analyzed by echocardiography. Results: The rabbit model of MI was established successfully. CD151 injection increased the expression of CD151 and microvessel density in the myocardium of MI rabbits. Heart function was significantly improved by CD151, which exhibited increased left ventricular ejection fraction, left ventricular fractional shortening and a reduced Tei index. Besides, US Sonovue significantly increased the expression efficiency of CD151. Conclusion: US microbubble was an effective vector for CD151 delivery. CD151 might be an effective therapeutic target for MI.

Objective: To explore the approach of minimally invasive transthoracic intramyocardial cellular transplantation under echocardiographic guidance to promote ischemic myocardial repair in a preclinical big-animal study. Methods: Female Guangxi Bama miniature pigs (weight: 25–30 kg) were randomly allocated into the sham group, untreated myocardial infarction (MI) group (MI group), the MI and surgical intramyocardial injection (SIM) group (MI-SIM group), and the MI and transthoracic echocardiography-guided percutaneous intramyocardial injection (TTEPIM) group (MI-TTEPIM group) (n = 4 each) using a lottery method. A swine MI model was established in the 3 groups excluding the sham group, and human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CM) labeled with the herpes simplex virus type-1 thymidine kinase reporter gene (hiPS-CMTK+) were transplanted by SIM in MI-SIM group and TTEPIM in MI-TTEPIM group. The operation time, postoperative recovery time of animals and volume of blood loss were collected for comparison between MI-SIM group and MI-TTEPIM group. 9-(4-[18F] fluoro-3-(hydroxymethyl) butyl) guanine positron emission tomography/computed tomography imaging was performed to track the hiPS-CMTK+ in vivo. Cardiac function and morphology were evaluated by echocardiography. Results: The operation time and postoperative recovery time of MI-TTEPIM group were significantly shorter than those of MI-SIM group ((28.3 ± 3.6) min vs. (97.0 ± 6.7) min, P &lt; 0.001; (1.3 ± 0.3) d vs. (7.5 ± 0.9) d, P &lt; 0.001). MI-TTEPIM also showed significantly lesser volume of blood loss during cell transplantation than MI-SIM group ((4.3 ± 0.8) mL vs. (47.0 ± 4.1) mL, P &lt; 0.001). The transplanted cells could be traced more accurately in vivo in MI-TTEPIM than in MI-SIM. The circumferential strain of intervention region in the MI-TTEPIM group (–25.07% ± 0.27%) was significantly higher than that of the MI-SIM (–20.39% ± 0.67%) and MI groups (–19.68% ± 0.67%), respectively (P &lt; 0.01). Conclusion: A minimally invasive TTEPIM protocol with stem cells for treating the ischemic myocardium was established in this study. Transplantation of hiPS-CMTK+ with this method could promote the recovery of the circumferential strain of the ischemic myocardium. The findings of this study lay a foundation for the clinical transformation of this auxiliary means of treatment in the future.

Objective: To investigate the effect of neuregulin-1(NRG-1) on cardiac glucose metabolism in Sprague Dawley (SD) rats with experimental myocardial infarction (MI). Methods: Adult male SD rats were randomly divided into three groups: the sham-operated group, MI group, and MI+NRG1 group. The rat MI model was established via ligation of the left anterior descending coronary artery. Two weeks after operation, echocardiography was performed, MI rats with left ventricular ejection fraction (LVEF) between 0.3-0.5 were selected and randomly assigned to MI group and MI+NRG-1 group. Rats in MI+NRG-1 group were treated with recombinant human NRG-1β (100 μg/kg) via tail vein at 2 weeks after operation (twice per week for 6 weeks); while rats in sham-operated group and MI group received equal volume of physiological saline. By the end of administration, echocardiography and small animal positron emission tomography (PET) were performed to detect cardiac function and myocardial glucose uptake. Myocardial morphology and collagen volume fraction, cardiomyocyte apoptosis and reactive oxygen species (ROS) production were evaluated by histopathologic analysis. Myocardial pyruvate dehydrogenase (PDH) and citrate synthase (CS) activity, as well as ATP production were detected by commercial kits. The mRNA and protein expression levels of NRG-1, p-ErbB4, and key factors involved in glucose metabolism (including Glut-4, HK2, PDK4, PDH, CS) were detected by quantitative real-time PCR (qRT-PCR) and Western blot assay, respectively. Results: With the MI model successfully established, the left ventricular ejection fraction(LVEF) and left ventricular shortening fraction(LVFS) were significantly lower in MI group and MI+NRG-1 group than that in sham group (both P<0.01), while there was no significant difference between MI group and MI+NRG-1 group(all P>0.05). After 6 weeks of NRG-1β intervention, the LVEF and LVFS were significantly higher in MI+NRG-1 group than in MI group (both P<0.01). By the end of experiment, PET imaging showed that the mean standardized uptake value (SUVmean) were lower in MI+NRG-1 group than in the sham group (4.06±0.28 vs. 5.18±0.37, P<0.01), while significantly higher than that in MI group (4.06±0.28 vs.2.86±0.49, P<0.01). Histopathological analysis showed that compared with MI group, rats in MI+NRG-1 group exhibited significantly decreased left ventricle collagen volume fraction ((7.83±1.24) % vs. (18.31±3.58) %, P<0.01), cardiomyocyte apoptosis((37.98±4.26)% vs. (67.04±5.38)%, P<0.01), and DHE fluorescence intensity(0.057 28±0.007 06 vs. 0.076 94±0.008 46, P<0.01), indicating that NRG-1β could reduce ROS production. PDH activity, CS activity, and ATP production were significantly higher in MI+NRG-1 group than in MI group (all P<0.05). qRT-PCR demonstrated an upregulated Glut-4, HK2 and CS, but downregulated PDK4 mRNA expression in MI+NRG-1 group compared with MI group (all P<0.01). Western blot assay showed significantly higher protein expression of NRG-1, p-ErbB4, Glut-4, HK2, PDH, CS in MI+NRG-1 group than in MI group (all P<0.01). Conclusion: NRG-1 could improve glucose uptake and utilization in myocardium by activating phosphorylation of myocardial ErbB4 receptor in MI rats, thus providing a therapeutic option for improving energy metabolism after MI.

Objective To explore the effect of hesperidin on cardiac function and ventricular remodeling following myocardial infarction (MI) in mice. Methods Ligation of left anterior descending (LAD) was operated to establish MI model. Forty-two C57BL/6 mice were randomly(random number) divided into control and MI group; and 24 h after LAD ligation, mice in MI group were further divided into MI control and hesperetin group. Eight weeks later, cardiac function and structure changes were determined by the methods of hemodynamic measurement and echocardiography. HE staining was used to measure cross-sectional area (CSA) of atrial myocytes, and PSR staining was applied for observe collagen deposition and calculation of collagen volume fraction (CVF). Real-time PCR was used to detect the mRNA expressions of cardiac hypertrophy markers (ANP, BNP and β-MHC) and cardiac fibrosis markers (Collagen Ⅰ, Collagen Ⅲ and CTGF). The contents of superoxide anion and hydroxy radical were detected by colorimetric method. Results Compared with control group, left ventricular posterior wall thickness (LVPWT) and inter-ventricular septum thickness (IVST) were increased to be thicker, left ventricular fractional shortening (LVFS) and left ventricular ejection fraction (LVEF) were significantly lower, and ±dp/dtmax was remarkably reduced in MI control group (P<0.05). Compared with MI control group, hesperetin could increase LVFS[(29.48±3.87)% vs. (20.69±3.99) %], LVEF [(46.40±1.68)% vs. (30.51±1.17) %] and ±dp/dtmax [(3 344.33±269.57)mmHg/S vs. (2 205.19±224.17)mmHg/S; (-2 250.40±218.35)mmHg/S vs. (-1 566.91±217.37) mmHg/S]; but could reduce LVPWT [(2.29±0.05)mm vs. (2.85±0.10) mm] and IVST [(1.44±0.09)mm vs.(1.89±0.06)mm]. Compared with control group, CSA and CVF were significantly increased in MI control mice. However, hesperetin could reduce CSA and CVF. Compared with control group, the mRNA expressions of cardiac hypertrophy and cardiac fibrosis markers were significantly increased in MI control mice; but hesperetin could significantly inhibit the mRNA expressions of cardiac hypertrophy and cardiac fibrosis markers. Additionally, hesperetin could significantly reduce the contents of superoxide anion and hydroxy radical. Conclusion Hesperetin intervention can inhibit ventricular structure change, and improve hemodynamics and cardiac function after acute myocardial infarction via inhibiting the production of reactive oxygen species (ROS). Key words: Hesperetin; Myocardial infarction; Cardiac function; Ventricular remodeling; Reactive oxygen species; Mice