Astaxanthin Alleviates the Process of Cardiac Hypertrophy by Targeting the METTL3/Circ_0078450/MiR-338-3p/GATA4 Pathway

Astaxanthin (ASX) is a natural antioxidant with preventive and therapeutic effects on various human diseases. However, the role of ASX in cardiac hypertrophy and its underlying molecular mechanisms remain unclear.Cardiomyocytes (AC16) were used with angiotensin-II (Ang-II) to mimic the cardiac hypertrophy cell model. The protein levels of hypertrophy genes, GATA4, and methyltransferase-like 3 (METTL3) were determined by western blot analysis. Cell size was assessed using immunofluorescence staining. The expression of circ_0078450, miR-338-3p, and GATA4 were analyzed by quantitative real-time PCR. Also, the interaction between miR-338-3p and circ_0078450 or GATA4 was confirmed by dual-luciferase reporter and RIP assays, and the regulation of METTL3 on circ_0078450 was verified by MeRIP and RIP assays.ASX reduced the hypertrophy gene protein expression and cell size in Ang-II-induced AC16 cells. Circ_0078450 was promoted under Ang-II treatment, and ASX reduced circ_0078450 expression in Ang-II-induced AC16 cells. Circ_0078450 could sponge miR-338-3p to positively regulate GATA4 expression, and GATA4 overexpression overturned the suppressive effect of circ_0078450 knockdown on Ang-II-induced cardiomyocyte hypertrophy. Also, the inhibitory effect of ASX on Ang-II-induced cardiomyocyte hypertrophy could be reversed by circ_0078450 or GATA4 overexpression. In addition, METTL3 mediated the m6A methylation of circ_0078450 to enhance circ_0078450 expression. Moreover, METTL3 knockdown suppressed Ang-II-induced cardiomyocyte hypertrophy by inhibiting circ_0078450 expression.Our data showed that ASX repressed cardiac hypertrophy by regulating the METTL3/circ_0078450/miR-338-3p/GATA4 axis.

Salidroside Ameliorates Ischemia/Reperfusion-Induced Human Cardiomyocyte Injury by Inhibiting the Circ_0097682/miR-671-5p/USP46 Pathway

Salidroside shows an inhibitory effect on myocardial ischemia/reperfusion (I/R) injury; however, the underlying mechanism remains to be explored. The present work analyzes the mechanism that drives salidroside to ameliorate I/R-induced human cardiomyocyte injury. Human cardiomyocytes were subjected to I/R treatment to simulate a myocardial infarction cell model. Cell viability, cell proliferation, and cell apoptosis were analyzed by CCK-8 assay, EdU assay, and flow cytometry analysis, respectively. RNA expression levels of circ_0097682, miR-671-5p, and F-box and ubiquitin-specific peptidase 46 (USP46) were detected by qRT-PCR. Protein expression was measured by Western blotting assay. The levels of IL-6, IL-1β, and TNF-α in cell supernatant were detected by enzyme-linked immunosorbent assays. Salidroside treatment relieved I/R-induced inhibitory effect on AC16 cell proliferation and promoting effects on cell apoptosis, inflammation, and oxidative stress. Salidroside inhibited circ_0097682 expression in I/R-treated AC16 cells. Salidroside-mediated inhibition of I/R-induced cell injury involved the downregulation of circ_0097682 expression. In addition, circ_0097682 bound to miR-671-5p in AC16 cells, and miR-671-5p inhibitors rescued salidroside pretreatment-mediated effects in I/R-treated AC16 cells. Moreover, miR-671-5p targeted USP46 in AC16 cells, and USP46 introduction partially relieved circ_0097682 depletion or salidroside pretreatment-induced effects in I/R-treated AC16 cells. Salidroside ameliorated I/R-induced AC16 cell injury by inhibiting the circ_0097682/miR-671-5p/USP46 pathway.

Molecular mechanisms of cardiotoxicity induced by acetamide and its chiral isomers

Acetamide (ACT) is used in a racemic form, and the considerable residues of this compound in the environment raise potential safety concerns for human health. We investigated the toxicity of ACT and its chiral isomers on human cardiomyocyte (AC16) cell line and zebrafish embryonic heart, and found that (+)-S-ACT was the main component causing cardiac toxicity. Our findings indicate that the IC50 of (±)-Rac-ACT on AC16 cells was 20.19 μg/mL. (-)-R-ACT, (±)-Rac-ACT, and (+)-S-ACT caused DNA damage and apoptosis in AC16 cells at this concentration. The underlying molecular mechanism may involve the induction of reactive oxygen species (ROS). The accumulation of ROS results in a decline in mitochondrial membrane potential (MMP) and prompts the release of cytochrome c (cyt c) from the mitochondria. This cascade of events ultimately activates the caspase-3 and caspase-9 signaling pathways, resulting in apoptosis. Furthermore, in vivo observations in zebrafish hearts demonstrated caspase-3 activation and the presence of the DNA damage marker (γH2AX), indicating that (+)-S-ACT is more toxic to cardiomyocytes than (-)-R-ACT and (±)-Rac-ACT. These findings suggest that (+)-S-ACT may be the primary component responsible for the toxicity of (±)-Rac-ACT in AC16 cells. Overall, these findings raise public awareness regarding the risks associated with chiral isomeric pesticides and provide a scientific foundation for their appropriate use.

Exosomal circ_HIPK3 reduces apoptosis in H2O2-induced AC16 cardiomyocytes through miR-33a-5p/IRS1 axis

BACKGROUND

Exosomal circular RNAs (circRNAs) has been revealed to participate in the processes of cellular angiogenesis, growth and metastasis. Herein, the goal of this work was to investigate the role of exosomal circ_HIPK3 in cardiomyocyte apoptosis.

METHODS

Exosomes were isolated using ultracentrifugation method and observed by transmission electron microscopy (TEM). Western blot was used to detect exosomes markers. The experimental group AC16 cells were exposed to hydrogen peroxide (H2O2). Levels of genes and proteins was detected by qRT-PCR and Western blot. EdU assay, CCK8 assay, flow cytometry, and Western blot were utilized to detect the function of exosomal circ_HIPK3 in proliferation, and apoptosis. The target relationship between miR-33a-5p and circ_HIPK3 or IRS1 (insulin receptor substrate 1).

RESULTS

Circ_HIPK3 was packaged into exosomes and derived from AC16 cells. The expression of circ_HIPK3 was decreased by H2O2 treatment in AC16 cells, which also led to the decrease of circ_HIPK3 in exosomes. Functional analysis showed exosomal circ_HIPK3 promoted AC16 cell proliferation and reduced cell apoptosis under H2O2 treatment. Mechanistically, circ_HIPK3 acted as a sponge of miR-33a-5p to up-regulate the expression of its target IRS1. Functionally, forced expression of miR-33a-5p reversed the reduction of exosomal circ_HIPK3 in apoptosis of H2O2-stimulated AC16 cells. Moreover, miR-33a-5p inhibition contributed to the proliferation of H2O2-stimulated AC16 cells, which was abolished by IRS1 silencing.

CONCLUSION

Exosomal circ_HIPK3 reduced H2O2-induced AC16 cardiomyocyte apoptosis through miR-33a-5p/IRS1 axis, suggesting a novel insight into the pathology of myocardial infarction.

Functional analysis of HECA variants identified in congenital heart disease in the Chinese population

Background

Congenital heart disease (CHD) is a class of cardiovascular defects that includes septal defects, outflow tract abnormalities, and valve defects. Human homolog of Drosophila headcase (HECA) is a novel cell cycle regulator whose role in CHD has not been elucidated. This is the first study to determine the frequency of HECA mutations in patients with CHD and the association between HECA variants and CHD.

Methods

In this study, we identified a candidate gene, HECA, by whole‐exome sequencing of an atrial septal defect family. To investigate the association between HECA variants and CHD risk, targeted exon sequencing was conducted in 689 individuals with sporadic CHD. We further analyzed the effect of HECA gene abnormalities on cardiomyocyte phenotype behavior and related signaling pathways by Western blotting, reverse transcription‐quantitative polymerase chain reaction, and scratch assay.

Results

We found a novel de novo mutation, c.409_410insA (p. W137fs), in the HECA gene and identified five rare deleterious variants that met the filtering criteria in 689 individuals with sporadic CHD. Fisher's exact test revealed a significant association between HECA variations and CHD compared with those in gnomADv2‐East Asians(p = 0.0027). Further functional analysis suggested that the variant p. W137fs resulted in a deficiency of the normal HECA protein, and HECA deficiency altered AC16 cell cycle progression, increased cell proliferation, and migration, and promoted the activation of the PDGF‐BB/PDGFRB/AKT pathway.

Conclusions

Our study identified HECA and its six rare variants, expanding the spectrum of genes associated with CHD pathogenesis in the Chinese population.

Calreticulin expression in human cardiac myocytes induces ER stress-associated apoptosis

The global burden of heart failure following myocardial ischemia-reperfusion (IR) injury is a growing problem. One pathway that is key to understanding the progression of myocardial infarction and IR injury is the endoplasmic reticulum (ER) stress pathway, which contributes to apoptosis signaling and tissue death. The role of calreticulin in the progression of ER stress remains controversial. We hypothesized that calreticulin induction drives proapoptotic signaling in response to ER stress. We find here that calreticulin is upregulated in human ischemic heart failure cardiac tissue, as well as simulated hypoxia and reoxygenation (H/R) and thapsigargin-mediated ER stress. To test the impact of direct modulation of calreticulin expression on ER stress-induced apoptosis, human cardiac-derived AC16 cells with stable overexpression or silencing of calreticulin were subjected to thapsigargin treatment, and markers of apoptosis were evaluated. It was found that overexpression of calreticulin promotes apoptosis, while a partial knockdown protects against the expression of caspase 12, CHOP, and reduces thapsigargin-driven TUNEL staining. These data shed light on the role that calreticulin plays in apoptosis signaling during ER stress in cardiac cells.