Investigating mitochondrial metabolism in contracting HL-1 cardiomyocytes following hypoxia and pharmacological HIF activation identifies HIF-dependent and independent mechanisms of regulation.

Abstract

Hypoxia is a consequence of cardiac disease and downregulates mitochondrial metabolism, yet the molecular mechanisms through which this occurs in the heart are incompletely characterized. Therefore, we aimed to use a contracting HL-1 cardiomyocyte model to investigate the effects of hypoxia on mitochondrial metabolism. Cells were exposed to hypoxia (2% O2) for 6, 12, 24, and 48 hours to characterize the metabolic response. Cells were subsequently treated with the hypoxia inducible factor (HIF)-activating compound, dimethyloxalylglycine (DMOG), to determine whether hypoxia-induced mitochondrial changes were HIF dependent or independent, and to assess the suitability of this cultured cardiac cell line for cardiovascular pharmacological studies. Hypoxic cells had increased glycolysis after 24 hours, with glucose transporter 1 and lactate levels increased 5-fold and 15-fold, respectively. After 24 hours of hypoxia, mitochondrial networks were more fragmented but there was no change in citrate synthase activity, indicating that mitochondrial content was unchanged. Cellular oxygen consumption was 30% lower, accompanied by decreases in the enzymatic activities of electron transport chain (ETC) complexes I and IV, and aconitase by 81%, 96%, and 72%, relative to controls. Pharmacological HIF activation with DMOG decreased cellular oxygen consumption by 43%, coincident with decreases in the activities of aconitase and complex I by 26% and 30%, indicating that these adaptations were HIF mediated. In contrast, the hypoxia-mediated decrease in complex IV activity was not replicated by DMOG treatment, suggesting HIF-independent regulation of this complex. In conclusion, 24 hours of hypoxia increased anaerobic glycolysis and decreased mitochondrial respiration, which was associated with changes in ETC and tricarboxylic acid cycle enzyme activities in contracting HL-1 cells. Pharmacological HIF activation in this cardiac cell line allowed both HIF-dependent and independent mitochondrial metabolic changes to be identified.

• Authors: Lucy J A Ambrose, Amira H Abd-Jamil, Renata S M Gomes, Emma E Carter, Carolyn A Carr, Kieran Clarke, Lisa C Heather
• Journal: Journal of cardiovascular pharmacology and therapeutics (J Cardiovasc Pharmacol Ther) Vol. 19 Issue 6 Pg. 574-85 (Nov 2014) ISSN: 1940-4034 [Electronic] United States
• PMID: 24607765 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © The Author(s) 2014.

Chemical References

• Amino Acids, Dicarboxylic
• Basic Helix-Loop-Helix Transcription Factors
• Glucose Transporter Type 1
• Hif1a protein, mouse
• Hypoxia-Inducible Factor 1, alpha Subunit
• RNA, Messenger
• Slc2a1 protein, mouse
• endothelial PAS domain-containing protein 1
• Lactic Acid
• Electron Transport Complex IV
• Aconitate Hydratase
• Electron Transport Complex I
• oxalylglycine

Topics

• Aconitate Hydratase (metabolism)
• Amino Acids, Dicarboxylic (pharmacology)
• Animals
• Basic Helix-Loop-Helix Transcription Factors (genetics, metabolism)
• Cell Hypoxia
• Cell Line
• Cell Respiration (drug effects)
• Electron Transport Complex I (metabolism)
• Electron Transport Complex IV (metabolism)
• Glucose Transporter Type 1 (agonists, metabolism)
• Glycolysis (drug effects)
• Hypoxia-Inducible Factor 1, alpha Subunit (genetics, metabolism)
• Lactic Acid (metabolism)
• Mice
• Mitochondria, Heart (drug effects, metabolism)
• Myocardial Contraction (drug effects)
• Myocytes, Cardiac (drug effects, metabolism)
• Oxygen Consumption (drug effects)
• RNA, Messenger (metabolism)
• Signal Transduction (drug effects)
• Time Factors
• Up-Regulation