The engulfment of a proto-mitochondrion by a primitive unicellular organism gave rise to the first eukaryotic cell, and ever since, mitochondrial function has been a vital aspect of eukaryotic life. Under conditions of physiological stress, the mitochondrion is far from a passive bystander, instead playing a key role in signalling pathways and the cellular responses they elicit. In this thematic series of Extreme Physiology & Medicine, the role of the mitochondrion in the response to physiological stress will be considered anew, through research articles, reviews, viewpoints and methodology papers that aim to reposition the organelle as a key player in the human response to a wide range of extreme conditions.
Alex’s notes: The endosymbiotic theory holds that a pioneering proto-mitochondrion entered a primitive host cell, taking up residence in the intracellular environment and thereby laying the foundations of eukaryotic life. The mitochondrion surrendered much of its genetic material, and thus executive control to the host cell, whilst the host delegated a number of key functions to the hopeful organelle, chiefly energy production via oxidative phosphorylation, but also catabolic and anabolic processes, apoptotic cell death and, to a degree, sex determination.
Indeed, preservation of mitochondrial function is quite literally vital to our survival, having been shown to correlate positively with outcome in the critically ill. It is perhaps, therefore, paradoxical to consider that this organelle, deemed to be so intricately linked with our own survival, also manages our eventual demise. As a significant possible source of ROS within our cells and their own proteins, lipids and unprotected DNA, such proximate targets of oxidative stress, the mitochondria may play a central role in the process of human ageing and ultimate energetic and functional decline.