CpG oligodeoxynucleotide preconditioning improves cardiac function after myocardial infarction via modulation of energy metabolism and angiogenesis.

Unmethylated CpG oligodeoxynucleotide (CpG-ODN), a Toll-like receptor 9 (TLR9) ligand, has been shown to protect against myocardial ischemia/reperfusion injury. However, the potential effects of CpG-ODN on myocardial infarction (MI) induced by persistent ischemia remains unclear. Here, we investigated whether and how CpG-ODN preconditioning protects against MI in mice. C57BL/6 mice were treated with CpG-ODN by i.p. injection 2 hr prior to MI induction, and cardiac function, and histology were analyzed 2 weeks after MI. Both 1826-CpG and KSK-CpG preconditioning significantly improved the left ventricular (LV) ejection fraction (LVEF) and LV fractional shortening (LVFS) when compared with non-CpG controls. Histological analysis further confirmed the cardioprotection of CpG-ODN preconditioning. In vitro studies further demonstrated that CpG-ODN preconditioning increases cardiomyocyte survival under hypoxic/ischemic conditions by enhancing stress tolerance through TLR9-mediated inhibition of the SERCA2/ATP and activation of AMPK pathways. Moreover, CpG-ODN preconditioning significantly increased angiogenesis in the infarcted myocardium compared with non-CpG. However, persistent TLR9 activation mediated by lentiviral infection failed to improve cardiac function after MI. Although CpG-ODN preconditioning increased angiogenesis in vitro, both the persistent stimulation of CpG-ODN and stable overexpression of TLR9 suppressed the tube formation of cardiac microvascular endothelial cells. CpG-ODN preconditioning significantly protects cardiac function against MI by suppressing the energy metabolism of cardiomyocytes and promoting angiogenesis. Our data also indicate that CpG-ODN preconditioning may be useful in MI therapy.

Genetic association analyses of fast plasma glucose level in pre-menopausal Chinese women: potential interaction between osteocalcin and oestrogen receptor α.

BACKGROUND: Fasting plasma glucose (FPG) levels are usually tightly regulated within a narrow physiologic range. Variation of FPG levels is clinically important and is strongly heritable. Several lines of evidence suggest the importance of the oestrogen receptor α (ER-α) and osteocalcin (also known as BGP, for bone Gla protein) in determining FPG; however, whether their polymorphisms are associated with FPG variation is not well understood. AIM: To investigate whether ER-a PvuII and BGP HindIII genetic polymorphisms and their potential interaction are associated with FPG variation. SUBJECTS AND METHODS: The study subjects were 328 unrelated pre-menopausal Chinese women aged 21 years and over (mean age ± SD, 33.2 ± 5.9 years), with an average FPG of 4.92 (SD = 0.81). All subjects were genotyped at the ER-α PvuII and BGP HindIII loci using polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP). RESULTS: The ER-α PvuII genotypes were significantly associated with FPG (p = 0.007). In addition, a significant interaction was observed of the ER-α PvuII polymorphism with BGP HindIII polymorphism on FPG variation (p = 0.013), although the BGP HindIII polymorphism was not shown to be individually associated with FPG. CONCLUSION: The PvuII polymorphism of the ER-α gene and its potential interaction with the HindIII polymorphism of the BGP gene were associated with FPG in pre-menopausal Chinese women.

Mettl3-mediated m6A modification of Fgf16 restricts cardiomyocyte proliferation during heart regeneration.

Cardiovascular disease is the leading cause of death worldwide due to the inability of adult heart to regenerate after injury. N6-methyladenosine (m6A) methylation catalyzed by the enzyme methyltransferase-like 3 (Mettl3) plays an important role in various physiological and pathological bioprocesses. However, the role of m6A in heart regeneration remains largely unclear. To study m6A function in heart regeneration, we modulated Mettl3 expression in vitro and in vivo. Knockdown of Mettl3 significantly increased the proliferation of cardiomyocytes and accelerated heart regeneration following heart injury in neonatal and adult mice. However, Mettl3 overexpression decreased cardiomyocyte proliferation and suppressed heart regeneration in postnatal mice. Conjoint analysis of methylated RNA immunoprecipitation sequencing (MeRIP-seq) and RNA-seq identified Fgf16 as a downstream target of Mettl3-mediated m6A modification during postnatal heart regeneration. RIP-qPCR and luciferase reporter assays revealed that Mettl3 negatively regulates Fgf16 mRNA expression in an m6A-Ythdf2-dependent manner. The silencing of Fgf16 suppressed the proliferation of cardiomyocytes. However, the overexpression of ΔFgf16, in which the m6A consensus sequence was mutated, significantly increased cardiomyocyte proliferation and accelerated heart regeneration in postnatal mice compared with wild-type Fgf16. Our data demonstrate that Mettl3 post-transcriptionally reduces Fgf16 mRNA levels through an m6A-Ythdf2-dependen pathway, thereby controlling cardiomyocyte proliferation and heart regeneration.

Cardiovascular diseases are one of the world's biggest killers. Even for patients who survive a heart attack, recovery can be difficult. This is because ­ unlike some amphibians and fish ­ humans lack the ability to produce enough new heart muscle cells to replace damaged tissue after a heart injury. In other words, the human heart cannot repair itself. Molecules known as messenger RNA (mRNA) carry the 'instructions' from the DNA inside the cell nucleus to its protein-making machinery in the cytoplasm of the cell. These messenger molecules can also be altered by different enzymes that attach or remove chemical groups. These modifications can change the stability of the mRNA, or even 'silence' it altogether by stopping it from interacting with the protein-making machinery, thus halting production of the protein it encodes. For example, a protein called Mettl3 can attach a methyl group to a specific part of the mRNA, causing a reversible mRNA modification known as m⁶A. This type of alteration has been shown to play a role in many conditions, including heart disease, but it has been unclear whether m⁶A could also be important for the regeneration of heart tissue. To find out more, Jiang, Liu, Chen et al. studied heart injury in mice of various ages. Newborn mice can regenerate their heart muscle for a short time, but adult mice lack this ability, which makes them a useful model to study heart disease. Analyses of the proteins and mRNAs in mouse heart cells confirmed that both Mettl3 and m⁶A-modified mRNAs were present. The amount of each also increased with age. Next, experiments in genetically manipulated mice revealed that removing Mettl3 greatly improved tissue repair after heart injury in both newborn and adult mice. In contrast, mouse hearts that produced abnormally high quantities of Mettl3 were unable to regenerate ­ even if the mice were young. Moreover, a detailed analysis of gene activity revealed that Mettl3 was suppressing heart regeneration by decreasing the production of a growth-promoting protein called FGF16. These results reveal a key biological mechanism controlling the heart's ability to repair itself after injury. In the future, Jiang et al. hope that Mettl3 can be harnessed for new, effective therapies to promote heart regeneration in patients suffering from heart disease.

Intraventricular flow visualization in different heart failure stages with blood pump support in a mock circulatory loop.

The intraventricular blood flow changed by blood pump flow dynamics may correlate with thrombosis and ventricular suction. The flow velocity, distribution of streamlines, vorticity, and standard deviation of velocity inside a left ventricle failing to different extents throughout the cardiac cycle when supported by an axial blood pump were measured by particle image velocimetry (PIV) in this study. The results show slower and static flow velocities existed in the central region of the left ventricle near the mitral valve and aortic valve and that were not sensitive to left ventricular (LV) failure degree or LV pressure. Strong vorticity located near the inner LV wall around the LV apex and the blood pump inlet was not sensitive to LV failure degree or LV pressure. Higher standard deviation of the blood velocity at the blood pump inlet decreased with increasing LV failure degree, whereas the standard deviation of the velocity near the atrium increased with increasing intraventricular pressure. The experimental results demonstrated that the risk of thrombosis inside the failing left ventricle is not related to heart failure degree. The "washout" performance of the strong vorticity near the inner LV wall could reduce the thrombotic potential inside the left ventricle and was not related to heart failure degree. The vorticity near the aortic valve was sensitive to LV failure degree but not to LV pressure. We concluded that the risk of blood damage caused by adverse flow inside the left ventricle decreased with increasing LV pressure.

Experimental investigation of the influence of the hydraulic performance of an axial blood pump on intraventricular blood flow.

Blood flow inside the left ventricle (LV) is a concern for blood pump use and contributes to ventricle suction and thromboembolic events. However, few studies have examined blood flow inside the LV after a blood pump was implanted. In this study, in vitro experiments were conducted to emulate the intraventricular blood flow, such as blood flow velocity, the distribution of streamlines, vorticity and the standard deviation of velocity inside the LV during axial blood pump support. A silicone LV reconstructed from computerized tomography (CT) data of a heart failure patient was incorporated into a mock circulatory loop (MCL) to simulate human systemic circulation. Then, the blood flow inside the ventricle was examined by particle image velocimetry (PIV) equipment. The results showed that the operating conditions of the axial blood pump influenced flow patterns within the LV and areas of potential blood stasis, and the intraventricular swirling flow was altered with blood pump support. The presence of vorticity in the LV from the thoracic aorta to the heart apex can provide thorough washing of the LV cavity. The gradually extending stasis region in the central LV with increasing blood pump support is necessary to reduce the thrombosis potential in the LV.

Forkhead box O3 protects the heart against paraquat-induced aging-associated phenotypes by upregulating the expression of antioxidant enzymes.

Paraquat (PQ) promotes cell senescence in brain tissue, which contributes to Parkinson's disease. Furthermore, PQ induces heart failure and oxidative damage, but it remains unknown whether and how PQ induces cardiac aging. Here, we demonstrate that PQ induces phenotypes associated with senescence of cardiomyocyte cell lines and results in cardiac aging-associated phenotypes including cardiac remodeling and dysfunction in vivo. Moreover, PQ inhibits the activation of Forkhead box O3 (FoxO3), an important longevity factor, both in vitro and in vivo. We found that PQ-induced senescence phenotypes, including proliferation inhibition, apoptosis, senescence-associated ß-galactosidase activity, and p16INK4a expression, were significantly enhanced by FoxO3 deficiency in cardiomyocytes. Notably, PQ-induced cardiac remolding, apoptosis, oxidative damage, and p16INK4a expression in hearts were exacerbated by FoxO3 deficiency. In addition, both in vitro deficiency and in vivo deficiency of FoxO3 greatly suppressed the activation of antioxidant enzymes including catalase (CAT) and superoxide dismutase 2 (SOD2) in the presence of PQ, which was accompanied by attenuation in cardiac function. The direct in vivo binding of FoxO3 to the promoters of the Cat and Sod2 genes in the heart was verified by chromatin immunoprecipitation (ChIP). Functionally, overexpression of Cat or Sod2 alleviated the PQ-induced senescence phenotypes in FoxO3-deficient cardiomyocyte cell lines. Overexpression of FoxO3 and CAT in hearts greatly suppressed the PQ-induced heart injury and phenotypes associated with aging. Collectively, these results suggest that FoxO3 protects the heart against an aging-associated decline in cardiac function in mice exposed to PQ, at least in part by upregulating the expression of antioxidant enzymes and suppressing oxidative stress.