Screening for Mitochondrial tRNA Mutations in 318 Patients with Dilated Cardiomyopathy.

OBJECTIVES: Dilated cardiomyopathy (DCM) is a complex cardiovascular disease with unknown etiology. Although nuclear genes play active roles in DCM, mitochondrial dysfunction was believed to be involved in the pathogenesis of DCM. The objective of this study is to analysis the association between mitochondrial tRNA (mt-tRNA) mutations and DCM. MATERIAL AND METHODS: We performed a mutational analysis of mt-tRNA genes in a cohort of 318 patients with DCM and 200 age- and gender-matched control subjects. To further assess their pathogenicity, phylogenetic analysis and mitochondrial functions including mtDNA copy number, ATP and ROS were analyzed. RESULTS: 7 possible pathogenic mutations: MT-TL1 3302A>G, MT-TI 4295A>G, MT-TM 4435A>G, MT-TA 5655T>C, MT-TH 12201T>C, MT-TE 14692A>G and MT-TT 15927G>A were identified in DCM group but absent in controls. These mutations occurred at extremely conserved nucleotides of corresponding tRNAs, and led to the failure in tRNAs metabolism. Moreover, a significant reduction in ATP and mtDNA copy number, whereas a markedly increased in ROS level were observed in polymononuclear leukocytes (PMNs) derived from the DCM patients carrying these mt-tRNA mutations, suggesting that these mutations may cause mitochondrial dysfunction that was responsible for DCM. CONCLUSIONS: Our data indicated that mt-tRNA mutations may be the molecular basis for DCM, which shaded novel insight into the pathophysiology of DCM that was manifestated by mitochondrial dysfunction.

Metformin ameliorates ferroptosis in cardiac ischemia and reperfusion by reducing NOX4 expression via promoting AMPKα.

CONTEXT: Metformin (Met) has a protective effect against cardiac ischemia and reperfusion (I/R) injury. OBJECTIVE: This study uncovered the Met effect on ferroptosis in cardiac I/R. MATERIALS AND METHODS: Sprague-Dawley rats underwent cardiac I/R treatment (ischaemia 30 min; reperfusion 24 h) (I/R group), and administered intravenously with Met (200 mg/kg) (I/R + Met group). Haematoxylin-eosin staining, Prussian blue staining, immunohistochemistry and transmission electron microscope were conducted on cardiac tissues. H9c2 cells underwent oxygen-glucose deprivation/reoxygenation (OGD/R group) and treated by Met (0.1 mM) (OGD/R + Met group). Adenosine monophosphate-activated protein kinase α (AMPKα) siRNA was transfected into OGD/R-induced H9c2 cells. Cell counting kit-8 (CCK-8) assay, dichloro-dihydro-fluorescein diacetate (DCFH-DA) and JC-1 staining were conducted on H9c2 cells. Ferroptosis-related indicators and gene expression were detected by enzyme-linked immunosorbent assay (ELISA), quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blot. RESULTS: In cardiac I/R rat, Met decreased heart and serum MDA, cardiac and serum non-heme iron, and serum CK-MB and LDH (inhibition rate: 50.0%, 48.8%, 47.6%, 29.5%, 30.6% and 34.7%, respectively), relieved cardiac tissue ferroptosis and mitochondria damage, increased fraction shortening and ejection fraction (157.5% and 146.2% on day 28, respectively), up-regulated AMPKα and down-regulated NOX4 in cardiac tissues. In OGD/R-induced H9c2 cells, Met (0.1 mM) increased cell viability (promotion rate: 170.0%), decreased non-heme iron and MDA (inhibition rate: 30.1% and 47.9%, respectively), relieved ferroptosis, up-regulated AMPKα and down-regulated NOX4. AMPKα silencing abrogated these effects of Met on the OGD/R-induced H9c2 cells. DISCUSSION AND CONCLUSIONS: Met shows effectiveness in relieving ferroptosis in cardiac I/R. In the future, Met may be an effective drug for relieving ferroptosis in cardiac I/R patients clinically.

Left ventricular thrombosis caused cerebral embolism during venoarterial extracorporeal membrane oxygenation support: A case report.

BACKGROUND: Venoarterial (VA) extracorporeal membrane oxygenation (ECMO), an effective short-term circulatory support method for refractory cardiogenic shock, is widely applied. However, retrospective analyses have shown that VA-ECMO-assisted cases were associated with a relatively high mortality rate of approximately 60%. Embolization in important organs caused by complications of left ventricular thrombosis (LVT) during VA-ECMO is also an important reason. Although the incidence of LVT during VA-ECMO is not high, the consequences of embolization are disastrous. CASE SUMMARY: A 37-year-old female patient was admitted to hospital because of fever for 4 d and palpitations for 3 d. After excluding the diagnosis of coronary heart disease, we established a diagnosis of "clinically explosive myocarditis". The patient still had unstable hemodynamics after drug treatment supported by VA-ECMO, with heparin for anticoagulation. On day 4 of ECMO support, a left ventricular thrombus attached to the papillary muscle root of the mitral valve was found by transthoracic echocardiography. Left ventricular decompression was performed and ECMO was successfully removed, but the patient eventually died of multiple cerebral embolism. CONCLUSION: LVT with high mobility during VA-ECMO may cause embolism in important organs. Therefore, a "wait and see" strategy should be avoided.

HDAC1 disrupts the tricarboxylic acid (TCA) cycle through the deacetylation of Nur77 and promotes inflammation in ischemia-reperfusion mice.

Histone deacetylase enzymes (HDACs) regulate protein acetylation. HDAC1 is known to enhance ischemia/reperfusion (I/R) injury, but its underlying mechanism(s) of action have not been defined. Here, in vivo mouse models of myocardial I/R were used to investigate the role of HDAC1 during I/R myocardial injury. We show that HDAC1 enhances the inflammatory responses of I/R mice. Using a constructed macrophage H/R (hypoxia/ regeneration) injury model (Raw264.7 cells), we identified Nur77 as a HDAC1 target in macrophages. Nur77 deficient macrophages failed to downregulate IDH1 (isocitrate dehydrogenase 1) and accumulated succinic acid and other tricarboxylic acid (TCA) cycle-derived metabolites in a glutamine-independent manner. These data show that the inhibition of HDAC1 ameliorates H/R-inflammation in macrophages through the regulation of Nur77 and the TCA cycle.

lncRNA NEAT1 Downregulation Ameliorates the Myocardial Infarction of Mice by Regulating the miR-582-5p/F2RL2 Axis.

Background: This study is aimed at effectively investigating the role of coagulation factor II thrombin receptor like 2 (F2RL2) in myocardial infarction (MI) as well as the upstream regulatory miRNA and lncRNA. Methods: Regulatory genes of F2RL2 were analyzed using StarBase and verified by dual-luciferase reporter assay. The MI mouse model was established. The left ventricular ejection fraction (EF) and fractional shortening (FS) were examined by echocardiography. The infarct area, pathological changes, and cell apoptosis in mouse myocardial tissue were evaluated using triphenyltetrazolium chloride and Evans blue, hematoxylin-eosin, and TUNEL staining assays. Oxygen-glucose deprivation- (OGD-) induced human cardiac myocytes (HCMs) were cultured and transfected. The cell viability, proliferation, and apoptosis were determined by CCK-8, EdU staining, and flow cytometry assays. The expressions of F2RL2, miR-582-5p, and nuclear paraspeckle assembly transcript 1 (NEAT1) in myocardial tissues and HCMs were quantified by qRT-PCR or Western blot. Results: NEAT1 sponged miR-582-5p which targeted F2RL2. NEAT1 and F2RL2 were highly expressed while miR-582-5p was lowly expressed in MI mice. F2RL2 downregulation prevented the reduction in EF and SF and the elevation in infarct area and cell apoptosis of MI mice. Both F2RL2 and NEAT1 downregulations reversely modulated the decreased viability and proliferation and the increased apoptosis of OGD-induced HCMs, while miR-582-5p inhibitor did oppositely. NEAT1 silencing upregulated miR-582-5p level but downregulated F2RL2 level. miR-582-5p inhibitor upregulated the F2RL2 level. The role of NEAT1 silencing in OGD-induced HCMs was reversed by miR-582-5p inhibitor whose effect was further offset by F2RL2 downregulation. Conclusion: NEAT1 downregulation ameliorates MI by regulating the miR-582-5p/F2RL2 axis, providing novel biomarkers for MI treatment.

MiR-193-3p attenuates the vascular remodeling in pulmonary arterial hypertension by targeting PAK4.

Pulmonary arterial hypertension (PAH) is a progressive pulmonary vascular disease associated with dysfunction of pulmonary artery endothelial cells and pulmonary artery smooth muscle cells (PASMCs). To explore the potential mechanism of miR-193-3p in pulmonary arterial hypertension, human PASMCs and rats were respectively stimulated by hypoxia and monocrotaline to establish PAH model in vivo and in vitro. The expressions of miR-193-3p and p21-activated protein kinase 4 (PAK4) in the lung samples of PAH patients and paired healthy samples from the healthy subjects in PHA cells and rats were detected by quantitative reverse transcriptase-PCR. Morphological changes in lung tissues were determined using hematoxylin and eosin staining. Right ventricular systolic pressure (RVSP) and ratio of right ventricle to left ventricle plus septum (RV/LV p S) were measured. The binding relationship between miR-193-3p and PAK4 was analyzed by TargetScan and verified by luciferase reporter assay. Cell viability, apoptosis, and migration were detected by 3-(4, 5-Dimethylthiazol-2- yl)-2,5-diphenyltetrazolium bromide (MTT) flow cytometry, and wound-healing assays, respectively. The protein expressions of PAK4, proliferating cell nuclear antigen (PCNA), P21, p-AKT, and AKT in vivo or in vitro were determined by Western blot. In this study, we found that in pulmonary arterial hypertension, miR-193-3p expression was downregulated and PAK4 expression was up-regulated. MiR-193-3p directly targeted PAK4 and negatively regulated its expression. Hypoxia condition promoted cell proliferation, migration, and inhibited apoptosis accompanied with increased expressions of PCNA and p-AKT/AKT and decreased expression of P21 in PASMCs. MiR-193-3p overexpression attenuated the effects of hypoxia on PASMCs via downregulating PAK4. Monocrotaline treatment increased p-AKT/AKT and decreased P21 expression and caused pulmonary vascular remodeling in the model rats. MiR-193-3p overexpression attenuated pulmonary vascular remodeling, decreased p-AKT/AKT, and increased P21 levels via downregulating PAK4 in monocrotaline-induced rats. The results in this study demonstrated that upregulation of miR-193-3p reduced cell proliferation, migration, and apoptosis of PAH in vitro and pulmonary vascular remodeling in PAH in vivo through downregulating PAK4.