Depletion of ubiA prenyltransferase domain containing 1 expression promotes angiotensin II‑induced hypertrophic response in AC16 human myocardial cells via modulating the expression levels of coenzyme Q10 and endothelial nitric oxide synthase

Systematic transcriptomic and phenotypic characterization of human and murine cardiac myocyte cell lines and primary cardiomyocytes reveals serious limitations and low resemblances to adult cardiac phenotype

BACKGROUND

Cardiac cell lines and primary cells are widely used in cardiovascular research. Despite increasing number of publications using these models, comparative characterization of these cell lines has not been performed, therefore, their limitations are undetermined. We aimed to compare cardiac cell lines to primary cardiomyocytes and to mature cardiac tissues in a systematic manner.

METHODS AND RESULTS

Cardiac cell lines (H9C2, AC16, HL-1) were differentiated with widely used protocols. Left ventricular tissue, neonatal primary cardiomyocytes, and human induced pluripotent stem cell-derived cardiomyocytes served as reference tissue or cells. RNA expression of cardiac markers (e.g. Tnnt2, Ryr2) was markedly lower in cell lines compared to references. Differentiation induced increase in cardiac- and decrease in embryonic markers however, the overall transcriptomic profile and annotation to relevant biological processes showed consistently less pronounced cardiac phenotype in all cell lines in comparison to the corresponding references. Immunocytochemistry confirmed low expressions of structural protein sarcomeric alpha-actinin, troponin I and caveolin-3 in cell lines. Susceptibility of cell lines to sI/R injury in terms of viability as well as mitochondrial polarization differed from the primary cells irrespective of their degree of differentiation.

CONCLUSION

Expression patterns of cardiomyocyte markers and whole transcriptomic profile, as well as response to sI/R, and to hypertrophic stimuli indicate low-to-moderate similarity of cell lines to primary cells/cardiac tissues regardless their differentiation. Low resemblance of cell lines to mature adult cardiac tissue limits their potential use. Low translational value should be taken into account while choosing a particular cell line to model cardiomyocytes.

Pyrroloquinoline quinone attenuates isoproterenol hydrochloride‑induced cardiac hypertrophy in AC16 cells by inhibiting the NF‑κB signaling pathway

Pyrroloquinoline quinone (PQQ) is a naturally occurring redox co-factor that functions as an essential nutrient and antioxidant, and has been reported to exert potent anti-inflammatory effects. However, the therapeutic potential of PQQ for isoproterenol hydrochloride (Iso)-induced cardiac hypertrophy has not yet been explored, at least to the best of our knowledge. In the present study, the anti-inflammatory effects of PQQ were investigated in Iso-treated AC16 cells, a myocardial injury cellular model characterized by an increase in the apparent surface area of the cells and the activation of intracellular cardiac hypertrophy-associated proteins. The results revealed that pre-treatment with PQQ significantly inhibited the expression of cardiac hypertrophy marker proteins, such as atrial natriuretic peptide, brain natriuretic peptide and β-myosin heavy chain. PQQ also inhibited the activation of the nuclear factor (NF)-κB signaling pathway in Iso-treated AC16 cells, thus inhibiting the nuclear translocation of NF-κB and reducing the phosphorylation levels of p65. On the whole, the findings of this study suggest that PQQ may be a promising therapeutic agent for effectively reversing the progression of cardiac hypertrophy.

Epigenome-Wide Association Study for All-Cause Mortality in a Cardiovascular Cohort Identifies Differential Methylation in Castor Zinc Finger 1 (CASZ1)

Background DNA methylation is implicated in many chronic diseases and may contribute to mortality. Therefore, we conducted an epigenome-wide association study (EWAS) for all-cause mortality with whole-transcriptome data in a cardiovascular cohort (CATHGEN [Catheterization Genetics]). Methods and Results Cases were participants with mortality≥7 days postcatheterization whereas controls were alive with≥2 years of follow-up. The Illumina Human Methylation 450K and EPIC arrays (Illumina, San Diego, CA) were used for the discovery and validation sets, respectively. A linear model approach with empirical Bayes estimators adjusted for confounders was used to assess difference in methylation (Δβ). In the discovery set (55 cases, 49 controls), 25 629 (6.5%) probes were differently methylated (P<0.05). In the validation set (108 cases, 108 controls), 3 probes were differentially methylated with a false discovery rate-adjusted P<0.10: cg08215811 (SLC4A9; log2 fold change=-0.14); cg17845532 (MATK; fold change=-0.26); and cg17944110 (castor zinc finger 1 [CASZ1]; FC=0.26; P<0.0001; false discovery rate-adjusted P=0.046-0.080). Meta-analysis identified 6 probes (false discovery rate-adjusted P<0.05): the 3 above, cg20428720 (intergenic), cg17647904 (NCOR2), and cg23198793 (CAPN3). Messenger RNA expression of 2 MATK isoforms was lower in cases (fold change=-0.24 [P=0.007] and fold change=-0.61 [P=0.009]). The CASZ1, NCOR2, and CAPN3 transcripts did not show differential expression (P>0.05); the SLC4A9 transcript did not pass quality control. The cg17944110 probe is located within a potential regulatory element; expression of predicted targets (using GeneHancer) of the regulatory element, UBIAD1 (P=0.01) and CLSTN1 (P=0.03), were lower in cases. Conclusions We identified 6 novel methylation sites associated with all-cause mortality. Methylation in CASZ1 may serve as a regulatory element associated with mortality in cardiovascular patients. Larger studies are necessary to confirm these observations.

UBIAD1 expression is associated with cardiac hypertrophy in spontaneously hypertensive rats

The present study investigated the potential role of UbiA prenyltransferase domain-containing 1 (UBIAD1) in the pathogenesis of hypertensive cardiac hypertrophy. Spontaneously hypertensive rats (SHRs) and Wistar‑Kyoto (WKY) rats at 8, 16 and 28 weeks of age were used. Blood pressure was measured using a non‑invasive tail cut‑off system. Cardiac functional index was assessed by arterial catheterization. Myocardial structure and cell apoptosis were evaluated by hematoxylin and eosin staining, and terminal deoxynucleotidyl‑transferase‑mediated dUTP nick end labeling assays, respectively. Myocardial expression of UBIAD1, coenzyme Q10 (CoQ10), endothelial nitric oxide synthase (eNOS) and atrial natriuretic peptide were evaluated by immunohistochemistry, western blotting and reverse transcription‑quantitative polymerase chain reaction. Circulating and myocardial expression of nitric oxide (NO) were measured using the Griess method. SHRs exhibited increased blood pressure and cardiomyocyte apoptosis, as well as cardiac hypertrophy, compared with age‑matched WKY rats. Myocardial expression of UBIAD1 was significantly decreased in SHRs in an age‑dependent manner. Similarly, myocardial CoQ10 and eNOS expression were significantly reduced in SHR compared to age‑matched WKY rats, and these expression levels additionally decreased further with aging. Serum and myocardial NO expression was additionally decreased in SHRs. Decreased UBIAD1 expression in SHR hearts was associated with decreased levels of CoQ10, eNOS and NO. Given the well‑established role of UBIAD1 in the regulation of NO signaling, reduced expression of UBIAD1 in SHR hearts potentially contributed to the pathogenesis of hypertensive cardiac hypertrophy. Therefore, UBIAD1 may represent a potential therapeutic target for clinical treatment of hypertensive cardiac hypertrophy.