Mitochondrial Stress Response in Neural Stem Cells Exposed to Electronic Cigarettes

https://www.sciencedirect.com/science/article/pii/S2589004219301713

Atena Zahedi, Rattapol Phandthong, Angela Chaili, Sara Leung, Esther Omaiye, Prue Talbot

A WORD ON MITOCHONDRIAL DYNAMICS (from this publication)

• Mitochondria of healthy cells continually divide and fuse with each other, forming an ever-changing mitochondrial network. This is referred to as mitochondrial dynamics.
• Fusion promotes exchange of mtDNA and other vital components, thus reinvigorating the mitochondrial network.
• Fission allows for disposal of faulty mitochondrial fragments through mitophagy. Moreover, when cells become committed to apoptosis, they shatter their mitochondrial networks.
• Modest levels of stress (well below the threshold to induce apoptosis) lead mitochondria to fuse extensively. This response was called stress‐induced mitochondrial hyperfusion (SIMH),  and might counter stress by optimizing mitochondrial ATP production.

FINDINGS OF THE PAPER

• Stem cells are critical to our wellbeing (controlling organ development and tissue renewal/repair) and the damage they accumulate over life can lead to disease.
• During development, neural stem cells are highly sensitive to toxicants and more vulnerable to stress than differentiated cells. Mitochondria are good indicators of stress in stem cells.
• Electronic cigarettes are marketed as a healthy substitute to cigarettes, and are targeted at youth and pregnant women.
• The authors exposed stem cells to EC fluid in a set of in vitro experiments. They argue that the nicotine present in EC fluid causes SIMH of stem cells. SIMH is a survival response in stem cells and is accompanied by increased oxidative stress and alterations in mitochondrial morphology and dynamics.
• Further, an interruption of autophagy was observed when stem cells were exposed to nicotine. Since autophagy is a defense mechanism of the cell, clearing damaged mitochondria, its inhibition is deleterious the the stem cell population.
• The main message of the study is that EC are not as harmless as they are claimed to be, and that similar findings could apply to any product containing nicotine.