Endotoxemia triggers life-threatening immune and cardiovascular response that leads to tissue damage, multi-organ failure, and death. The understanding of underlying molecular mechanisms is still evolving. N6-methyladenosine (m6A) RNA modification plays key regulatory role in numerous biological processes. However, it remains unclear whether endotoxemia alters RNA methylation in the myocardium. In the current study, we investigated the effect of LPS-induced endotoxemia on m6A-RNA methylation and its implications on myocardial inflammation and left ventricular (LV) function. Following LPS administration, mice showed increases in m6A-RNA methylation in the myocardium with a corresponding decrease in the expression of Fat mass and obesity-associated protein (FTO, an m6A eraser/demethylase). The changes were associated with a significant increase in expression of myocardial inflammatory cytokine genes, such as IL-6, TNF-α, IL-1β, and reduced LV function. Moreover, rat cardiomyoblasts (H9c2) exposed to LPS showed similar changes (with increase in m6A-RNA methylation and inflammatory cytokine genes, whereas downregulation of FTO). Furthermore, methylated RNA immunoprecipitation (MeRIP) assay showed hypermethylation and increase in the expression of IL-6 and TNF-α genes in LPS-treated H9c2 cells as compared to untreated cells. Interestingly, FTO knockdown in cardiomyocytes mimicked the above effects. Taken together, these data suggest that endotoxemia-induced m6A methylation might play a critical role in expression of cardiac proinflammatory cytokines, and modulation of m6A methylation might limit myocardial inflammation and dysfunction during endotoxemia.

Background: N6-methyladenosine (m6A) methylation is one of the important posttranscriptional modification of RNA, which affects RNA splicing, translation and stability. These modifications are dynamically regulated by writers, readers and erasers, and their alteration affects m6A modification and have shown to play key regulatory role in numerous biological processes. Fat mass- and obesity-associated (FTO) gene, known as a nucleic acid demethylase removes the methyl group from RNA and has been shown to be associated with progression of heart diseases. In this study, we determined m6A methylation in human failing heart, and evaluated if FTO regulates m6A-methylation of transcripts related to inflammation in cultured rat cardiomyocytes under various stress conditions. Methods and Results: m6A RNA-methylation was increased in human failing hearts as compared to heart samples from non-failing subjects. Interestingly, failing hearts were associated with significant decrease in FTO mRNA and protein expression. Furthermore, cultured rat cardiomyoblasts (H9C2) cells exposed to stressors (hypoxia or isoproterenol) for 24hrs showed significant decrease of FTO and an associated increase in m6A-RNA methylation (dot blot analysis). To further test if stress-induced increase in m6A-RNA modification is mediated through FTO, we knocked-down FTO, treated with isoproterenol for 24hrs and evaluated m6A methylation status of RNA. Interestingly, dot blot analysis showed significant increase in m6A methylation levels and proinflammatory cytokines (IL6 and TNFa) in FTO knockdown cells as compared to scramble, both at basal level and after exposure to stress. Furthermore, we evaluated the effect of FTO on methylation of RNA transcripts that encode inflammatory cytokines. MeRIP assay (Methylated RNA immunoprecipitation using m6A antibody and analysis of m6A-transcript by qRT-PCR) demonstrated that the gene expression of proinflammatory cytokines, IL6 and TNF-alpha was significantly increased in FTO knockdown cells as compared to scramble control cells . Conclusion: This data suggests stress-induced loss of FTO in the heart might mediate m6A-RNA methylation and therefore potential leading to upregulation of inflammatory response in the myocardium.

Medullary thyroid cancer (MTC) is a type of neuroendocrine cancer (NE) with increasing incidence worldwide. Compared with well-differentiated thyroid cancers, distant metastases are more commonly observed in MTC patients, ranging from 7-23%. The inability to treat metastatic MTC contributes to a decreased patient survival rate. Currently, at least nine mammalian voltage-gated sodium channels (VGSCs) named Nav1.1-Nav1.9 have been identified as potential safe drug targets for treating metastasis in various cancers. Herein, we investigate the effects of targeting VGSCs in MTC using small molecule inhibitors. Two MTC cell lines, TT and MZ, were treated with four compounds and the changes in mRNA and protein expression of VGSC isoform Nav1.7 were assessed through RT-PCR and western blotting. Treatment by one of the compounds exhibited a 28-fold decrease in mRNA expression of VGSC isoform 1.7. Furthermore, a cell proliferation assay, proliferation assay (MTT) a MTT, assay to study cell proliferation after treatment showed decreasing cell viability resulted from the treatment. and Additionally, morphological changes characteristic of apoptosis in fluorescently labeled MTC cell lines after 48 hours of treatment with VGSC inhibitory compounds were observed. A Boyden chamber assay was also performed on MTC cell lines to examine changes in migration and invasion after administering the potential inhibitory compounds. This study has generated preliminary evidence that voltage-gated sodium channels (VGSCs) may indeed be potential targets for treating metastatic MTC. The results may be translated to future studies focused on controlling metastasis through specified drug treatment in MTC, leading to the limitation of cancer progression by means of targeting VGSCs. Citation Format: Paras Ahuja, Rachael Guenter, Jaden Cowan, Yazen Shihab, Jason Whitt, Herbert Chen, Sadanandan Velu, Renata Jaskula-Sztul. Inhibiting voltage-gated sodium channel activity in medullary thyroid cancer using small molecule compounds [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2001.

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