The key role of microtubules in hypoxia preconditioning-induced nuclear translocation of HIF-1α in rat cardiomyocytes

Abstract

BackgroundHypoxia-inducible factor (HIF)-1 is involved in the regulation of hypoxic preconditioning in cardiomyocytes. Under hypoxic conditions, HIF-1α accumulates and is translocated to the nucleus, where it forms an active complex with HIF-1β and activates transcription of approximately 60 kinds of hypoxia-adaptive genes. Microtubules are hollow tubular structures in the cell that maintain cellular morphology and that transport substances. This study attempted to clarify the role of microtubule structure in the endonuclear aggregation of HIF-1α following hypoxic preconditioning of cardiomyocytes.MethodsPrimary rat cardiomyocytes were isolated and cultured. The cardiomyocyte culture system was used to establish a hypoxia model and a hypoxic preconditioning model. Interventions were performed on primary cardiomyocytes using a microtubule-depolymerizing agent and different concentrations of a microtubule stabilizer. The microtubule structure and the degree of HIF-1α nuclear aggregation were observed by confocal laser scanning microscopy. The expression of HIF-1α in the cytoplasm and nucleus was detected using Western blotting. Cardiomyocyte energy content, reflected by adenosine triphosphate/adenosine diphosphate (ATP/ADP), and key glycolytic enzymes were monitored by colorimetry and high-performance liquid chromatography (HPLC). Reactive oxygen species (ROS) production was also used to comprehensively assess whether microtubule stabilization can enhance the myocardial protective effect of hypoxic preconditioning.ResultsDuring prolonged hypoxia, it was found that the destruction of the microtubule network structure of cardiomyocytes was gradually aggravated. After this preconditioning, an abundance of HIF-1α was clustered in the nucleus. When the microtubules were depolymerized and hypoxia pretreatment was performed, HIF-1α clustering occurred around the nucleus, and HIF-1α nuclear expression was low. The levels of key glycolytic enzymes were significantly higher in the microtubule stabilizer group than in the hypoxia group. Additionally, the levels of lactate dehydrogenase and ROS were significantly lower in the microtubule stabilizer group than in the hypoxia group.ConclusionThe microtubules of cardiomyocytes may be involved in the process of HIF-1α endonuclear aggregation, helping to enhance the anti-hypoxic ability of cardiomyocytes.

Role of HIF1α Regulatory Factors in Stem Cells

“…Conversely, other studies have reported that hypoxia reduces microtubule stability and polymerization (95, 96). Despite these conflicting results, other studies have shown that stabilizing microtubules during hypoxia is critical for the nuclear translocation of HIF1 α and for enhancing the chemoresistance of tumor cells (97–99). Chronic hypoxia suppresses the nuclear translocation of HIF1 α by disrupting the microtubule network, which can be recovered by taxol (a microtubule stabilizer) pretreatment (97).…”

“…Despite these conflicting results, other studies have shown that stabilizing microtubules during hypoxia is critical for the nuclear translocation of HIF1 α and for enhancing the chemoresistance of tumor cells (97–99). Chronic hypoxia suppresses the nuclear translocation of HIF1 α by disrupting the microtubule network, which can be recovered by taxol (a microtubule stabilizer) pretreatment (97). In addition, stabilized microtubule inhibits Ran-mediated VHL nuclear translocation, leading to the stabilization of HIF1 α in the nucleus (100).…”

O-cyclic phytosphingosine-1-phosphate stimulates HIF1α-dependent glycolytic reprogramming to enhance the therapeutic potential of mesenchymal stem cells

“…HIF1 is activated through strict control of its alpha subunit (HIF1α) by transcription, translation, posttranslational modification like prolyl-or asparaginyl hydroxylation and ubiquitination, and microtubule-associated nuclear transportation. However, the HIF1 beta subunit (HIF1β) is constitutively expressed and does not possess an oxygen-dependent degradation domain [31][32][33][34] . Therefore, it has been suggested that HIF1α plays an important role in the HIF1-regulated metabolism.…”

Regulation of theβ-Adrenergic Receptor Signaling Pathway in Sustained Ligand-Activated Preconditioning

“…Protective GPCR signaling involves interaction with G proteins to communicate extracellular messages to intracellular effectors such as phospholipase C, AC, and ion channels (Eschenhagen, 1993;Novotny and Svoboda, 1998;Novotny et al, 1999Novotny et al, , 2001. In addition, activated Ga s acts as an intracellular messenger to modulate microtubule dynamics (Yu et al, 2009), key to cell morphology and intracellular signaling, and is implicated in preconditioning (Guo et al, 2017). Curiously, prior work implicated both stimulatory Ga s and inhibitory G i proteins in SLP protection (Peart and Gross, 2006), whereas acute morphine protection appears to be G i mediated.…”