| Summary: | In hepatocytes, ursodeoxycholic acid (UDCA) activates cell signalling pathways such as p53, intracellular calcium ([Ca2+]i), and sphingosine-1-phosphate (S1P)-receptor via Gαi-coupled-receptor. Recently, UDCA has been shown to protect the heart against hypoxia-reoxygenation injury. However, it is not clear whether UDCA cardioprotection against hypoxia acts through a transcriptional mediator of cells stress, HIF-1α and p53. Therefore, in here, we aimed to investigate whether UDCA could protect cardiomyocytes (CMs) against hypoxia by regulating expression of HIF-1α, p53, [Ca2+]i, and S1P-Gαi-coupled-receptor. Cardiomyocytes were isolated from newborn rats (0-2 days), and hypoxia was induced by using cobalt chloride (CoCl2). Cardiomyocytes were treated with UDCA and cotreated with either FTY720 (S1P-receptor agonist) or pertussis toxin (PTX; Gαi inhibitor). Cells were subjected for proliferation assay, beating frequency, QuantiGene Plex assay, western blot, immunofluorescence, and calcium imaging. Our findings showed that UDCA counteracted the effects of CoCl2 on cell viability, beating frequency, HIF-1α, and p53 protein expression. We found that these cardioprotection effects of UDCA were similar to FTY720, S1P agonist. Furthermore, we observed that UDCA protects CMs against CoCl2-induced [Ca2+]i dynamic alteration. Pharmacological inhibition of the Gαi-sensitive receptor did not abolish the cardioprotection of UDCA against CoCl2 detrimental effects, except for cell viability and [Ca2+]i. Pertussis toxin is partially effective in inhibiting UDCA protection against CoCl2 effects on CM cell viability. Interestingly, PTX fully inhibits UDCA cardioprotection on CoCl2-induced [Ca2+]i dynamic changes. We conclude that UDCA cardioprotection against CoCl2-induced hypoxia is similar to FTY720, and its actions are not fully mediated by the Gαi-coupled protein sensitive pathways. Ursodeoxycholic acid is the most hydrophilic bile acid and is currently used to treat liver diseases. Recently, UDCA is shown to have a cardioprotection effects; however, the mechanism of UDCA cardioprotection is still poorly understood. The current data generated were the first to show that UDCA is able to inhibit the activation of HIF-1α and p53 protein during CoCl2-induced hypoxia in cardiomyocytes. This study provides an insight of UDCA mechanism in protecting cardiomyocytes against hypoxia. Copyright © 2017 John Wiley & Sons, Ltd.
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