Ethyl isopropyl amiloride decreases oxidative phosphorylation and increases mitochondrial fusion in clonal untransformed and cancer cells.

Abstract

Many cancer cells, regardless of their tissue origin or genetic landscape, have increased expression or activity of the plasma membrane Na-H exchanger NHE1 and a higher intracellular pH (pHi) compared with untransformed cells. A current perspective that remains to be validated is that increased NHE1 activity and pHi enable a Warburg-like metabolic reprogramming of increased glycolysis and decreased mitochondrial oxidative phosphorylation. We tested this perspective and find it is not accurate for clonal pancreatic and breast cancer cells. Using the pharmacological reagent ethyl isopropyl amiloride (EIPA) to inhibit NHE1 activity and decrease pHi, we observe no change in glycolysis, as indicated by secreted lactate and intracellular pyruvate, despite confirming increased activity of the glycolytic enzyme phosphofructokinase-1 at higher pH. Also, in contrast to predictions, we find a significant decrease in oxidative phosphorylation with EIPA, as indicated by oxygen consumption rate (OCR). Decreased OCR with EIPA is not associated with changes in pathways that fuel oxidative phosphorylation or with mitochondrial membrane potential but occurs with a change in mitochondrial dynamics that includes a significant increase in elongated mitochondrial networks, suggesting increased fusion. These findings conflict with current paradigms on increased pHi inhibiting oxidative phosphorylation and increased oxidative phosphorylation being associated with mitochondrial fusion. Moreover, these findings raise questions on the suggested use of EIPA-like compounds to limit metabolic reprogramming in cancer cells.

• Authors: Sagar S Manoli, Kyle Kisor, Bradley A Webb, Diane L Barber
• Journal: American journal of physiology. Cell physiology (Am J Physiol Cell Physiol) Vol. 321 Issue 1 Pg. C147-C157 (07 01 2021) ISSN: 1522-1563 [Electronic] United States
• PMID: 34038242 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Epithelial Sodium Channel Blockers
• SLC9A1 protein, human
• Sodium-Hydrogen Exchanger 1
• Lactic Acid
• Amiloride
• Pyruvic Acid
• Phosphofructokinase-1
• ethylisopropylamiloride

Topics

• Amiloride (analogs & derivatives, pharmacology)
• Cell Line
• Cell Line, Tumor
• Clone Cells
• Epithelial Cells (cytology, drug effects, metabolism)
• Epithelial Sodium Channel Blockers (pharmacology)
• Gene Expression
• Glycolysis (genetics)
• Humans
• Hydrogen-Ion Concentration
• Lactic Acid (metabolism)
• Membrane Potential, Mitochondrial (drug effects)
• Mitochondria (drug effects, metabolism)
• Mitochondrial Dynamics (drug effects)
• Oxidative Phosphorylation (drug effects)
• Oxygen Consumption (drug effects)
• Phosphofructokinase-1 (genetics, metabolism)
• Pyruvic Acid (metabolism)
• Sodium-Hydrogen Exchanger 1 (antagonists & inhibitors, genetics, metabolism)