Assessing the translatability of in vivo cardiotoxicity mechanisms to in vitro models using causal reasoning

UR-144, synthetic cannabinoid receptor agonist, induced cardiomyoblast toxicity mechanism comprises cytoplasmic Ca2+ and DAPK1 related autophagy and necrosis

UR-144, a cannabinoid receptor agonist, is widely used alone or in combination with other synthetic cannabinoids (SCs) all over the world. At overdose, cardiovascular symptoms have been reported and the underlying molecular mechanisms of these adverse effects are not known. It is highly important to clarify the toxic effects of UR-144 for the treatment of poisoning. In the present study, the molecular mechanism of cytotoxic effects of UR-144 is evaluated on a cardiomyoblastic cell line using WST-1 and LDH assays. Apoptosis/necrosis, autophagy, and ROS (reactive oxygen species) levels were determined using flow cytometry. Cytoplasmic Ca²⁺ levels were measured by using a fluorogenic calcium-binding dye. Released and cytoplasmic troponin T levels, a specific marker of cardiotoxicity, were examined with western blot. For the evaluation of the role of DAPK1, on UR-144-induced cell death, DAPK1 activity and DAPK1 protein level were investigated. Its cytotoxic effects increased in a dose-dependent manner for WST-1 and LDH assays, while membrane damage, one of the signs of necrotic cell death, was more remarkable than damage to mitochondria. Cytoplasmic Ca²⁺ levels rose after high-dose UR-144 treatment and inhibition of DAPK1 activity ameliorated UR-144-induced cytotoxicity. Released troponin T significantly increased at a dose of 200 µM. ROS and total antioxidant capacity of cells were both reduced following high dose UR-144 treatment. The results indicated that UR-144-induced autophagic and necrotic cell death might be a consequence of elevated cytoplasmic Ca²⁺ levels and DAPK1 activation. However, in vivo/clinical studies are needed to identify molecular mechanisms of cardiotoxic effects of UR-144.

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.

Roflumilast Attenuates Doxorubicin-Induced Cardiotoxicity by Targeting Inflammation and Cellular Senescence in Cardiomyocytes Mediated by SIRT1

Background and Purpose

Cardiotoxicity is an important side effect of the treatment of a malignant tumor with Doxorubicin. Currently, decreasing the dosage of Doxorubicin to alleviate the side effects on cardiac function is the common method to deal with the cardiotoxicity induced by Doxorubicin. The present study aims to investigate the therapeutic effects of Roflumilast on Doxorubicin-induced inflammation and cellular senescence, as well as the potential mechanism in H9c2 myocardial cells.

Methods

The injured cardiac cell model was established by incubation with 5 μmol/L Doxorubicin. MTT was used to evaluate the cell viability of treated H9c2 cardiac cells. The expression of 4-HNE was determined using an immunofluorescence assay. The gene expression levels of IL-17, IL-6, TNF-α, IL-4, PAI-1, p21, and SIRT1 were evaluated using qRT-PCR and the protein levels of Gpx4, PAI-1, p21, and SIRT1 were determined using Western blot analysis. Secretions of IL-17, IL-6, TNF-α, IL-4, CK-MB, and cTnI were measured using ELISA. Cellular senescence was assessed using SA-β-Gal staining. Si-RNA technology was used to knockdown the expression of SIRT1 in H9c2 cardiac cells.

Results

Cell viability of H9c2 cardiac cells was significantly inhibited by Doxorubicin but rescued by Roflumilast. The upregulated 4-HNE and downregulated Gpx4 were reversed by Roflumilast. The secretions of IL-6 and IL-17 were promoted by Doxorubicin and suppressed by Roflumilast. The increased SA-β-Gal staining induced by Doxorubicin was inhibited by Roflumilast. P21 and PAI-1 were significantly upregulated and SIRT1 was greatly downregulated by Doxorubicin, all of which were reversed by Roflumilast. The anti-senescent effect of Roflumilast was abolished by knocking down SIRT1.

Conclusion

Roflumilast might attenuate Doxorubicin-induced inflammation and cellular senescence in cardiomyocytes by upregulating SIRT1.

Proteomics Analysis of Trastuzumab Toxicity in the H9c2 Cardiomyoblast Cell Line and its Inhibition by Carvedilol

OBJECTIVE

Heart dysfunctions are the major complications of trastuzumab in patients with Human Epidermal growth factor Receptor-2 (HER2)-positive breast cancers.

METHODS

In this study, the cytotoxicity of trastuzumab on H9c2 cardiomyoblasts was demonstrated, and the proteome changes of cells were investigated by a tandem mass tagging quantitative approach. The Differentially Abundant Proteins (DAPs) were identified and functionally enriched.

RESULTS

We determined that carvedilol, a non-selective beta-blocker, could effectively inhibit trastuzumab toxicity when administrated in a proper dose and at the same time. The proteomics analysis of carvedilol co-treated cardiomyoblasts showed complete or partial reversion in expressional levels of trastuzumab-induced DAPs.

CONCLUSION

Downregulation of proteins involved in the translation biological process is one of the most important changes induced by trastuzumab and reversed by carvedilol. These findings provide novel insights to develop new strategies for the cardiotoxicity of trastuzumab.

Identification of in vitro and in vivo disconnects using transcriptomic data

BACKGROUND

Integrating transcriptomic experiments within drug development is increasingly advocated for the early detection of toxicity. This is partly to reduce costs related to drug failures in the late, and expensive phases of clinical trials. Such an approach has proven useful both in the study of toxicology and carcinogenicity. However, general lack of translation of in vitro findings to in vivo systems remains one of the bottle necks in drug development. This paper proposes a method for identifying disconnected genes between in vitro and in vivo toxicogenomic rat experiments. The analytical framework is based on the joint modeling of dose-dependent in vitro and in vivo data using a fractional polynomial framework and biclustering algorithm.

RESULTS

Most disconnected genes identified belonged to known pathways, such as drug metabolism and oxidative stress due to reactive metabolites, bilirubin increase, glutathion depletion and phospholipidosis. We also identified compounds that were likely to induce disconnect in gene expression between in vitro and in vivo toxicogenomic rat experiments. These compounds include: sulindac and diclofenac (both linked to liver damage), naphtyl isothiocyanate (linked to hepatoxocity), indomethacin and naproxen (linked to gastrointestinal problem and damage of intestines).

CONCLUSION

The results confirmed that there are important discrepancies between in vitro and in vivo toxicogenomic experiments. However, the contribution of this paper is to provide a tool to identify genes that are disconnected between the two systems. Pathway analysis of disconnected genes may improve our understanding of uncertainties in the mechanism of actions of drug candidates in humans, especially concerning the early detection of toxicity.

Comparison of hepatic transcription profiles of locked ribonucleic acid antisense oligonucleotides: evidence of distinct pathways contributing to non-target mediated toxicity in mice

Development of LNA gapmers, antisense oligonucleotides used for efficient inhibition of target RNA expression, is limited by non-target mediated hepatotoxicity issues. In the present study, we investigated hepatic transcription profiles of mice administered non-toxic and toxic LNA gapmers. After repeated administration, a toxic LNA gapmer (TS-2), but not a non-toxic LNA gapmer (NTS-1), caused hepatocyte necrosis and increased serum alanine aminotransferase levels. Microarray data revealed that, in addition to gene expression patterns consistent with hepatotoxicity, 17 genes in the clathrin-mediated endocytosis (CME) pathway were altered in the TS-2 group. TS-2 significantly down-regulated myosin 1E (Myo1E), which is involved in release of clathrin-coated pits from plasma membranes. To map the earliest transcription changes associated with LNA gapmer-induced hepatotoxicity, a second microarray analysis was performed using NTS-1, TS-2, and a severely toxic LNA gapmer (HTS-3) at 8, 16, and 72 h following a single administration in mice. The only histopathological change observed was minor hepatic hypertrophy in all LNA groups across time points. NTS-1, but not 2 toxic LNA gapmers, increased immune response genes at 8 and 16 h but not at 72 h. TS-2 significantly perturbed the CME pathway only at 72 h, while Myo1E levels were decreased at all time points. In contrast, HTS-3 modulated DNA damage pathway genes at 8 and 16 h and also modulated the CME pathway genes (but not Myo1E) at 16 h. Our results may suggest that different LNAs modulate distinct transcriptional genes and pathways contributing to non-target mediated hepatotoxicity in mice.