Effects Of Microtubule Changes On The Glycolytic Pathway And Its Mechanism In Cardiomyocytes Inflicted By Hypoxia

Aims Hypoxia is one of the important pathophysiolgical phenomena in many disease processes,and hypoxia inducible factor(HIF)-1αis a key regulator of anaerobic energy metabolism in hypoxic cells. The present study is designed to investigate that cytoskeleton change affects glycolysis under hypoxia and breakdown of microtubular structures influences glycolysis in early hypoxic cardiomyocytes through regulating HIF-1αactivity and distribution in cells.Materials and methods1. To establish neonatal rat cardiomyocytes cultured model. Neonatal rat cardiomyocytes were cultured and treated with normoxia, hypoxia, a microtubule stabilizing agent or a microtubule depolymerizing agent which were used to establish the model for high expression of microtubule-associated protein 4 and the model for RNA interference-caused low expression of microtubulin.2. The microtubular structural changes and intracellular distribution of HIF-1αprotein were observed under laser confocal scanning microscopy. The cell survival was determined by Trypan blue stain. The activity of key glycolytic enzymes, creatine kinase, lactic acid, viability and energy production of cardiomyocyte were determined by colorimetry and high-performance liquid chromatography.3. The content of HIF-1αprotein following microtubular structural change was examined by Western blotting, and HIF-1αmRNA expression was determined by real-time PCR assay.Results1. During the earlier time of hypoxia, microtubular structures were broken in cardiomyocytes. Then the viability of cardiomyocytes and myocardial cell survival decreased. The stablilization of microtubule enhanced the viability of cardiomyocytes and myocardial cell survival.2. Disorganization of microtubular structures inhibited the activity of key glycolytic enzymes, and contents of lactic acid and ATP decreased during the earlier time of hypoxia. The microtubule stabilizing agent stabilized the reticular microtubular structures in hypoxic cardiomyocytes, increased the activity of key glycolytic enzymes, ameliorated cell energy supply and viability,3. During the earlier time of hypoxia, disorganization of microtubule structures inhibited the expression of HIF-1αand HIF-1αendonuclear aggregation. The microtubule stabilizing agent and high expression of microtubule-associated protein 4 upregulated HIF-1αprotein expression and endonuclear aggregation. In contrast, the microtubule -depolymerizing agent or knock-down of microtubulin expression aggravated breakdown of microtubular structures of hypoxic cardiomyocytes, further decreased HIF-1αprotein contents and endonuclear aggregation.Conclusions Microtubular structural changes influence glycolysis of early hypoxic cardiomyocytes by regulating HIF-1αactivity. Stabilizing microtubular structures increases endonuclear and total HIF-1αexpression, the activity of key glycolytic enzymes and energy supply. These findings provide potential therapeutic targets for ameliorating cell energy metabolism during early hypoxia.