57 5.3: The Role of Calcium

Intracellular calcium in mitochondria regulates various cellular functions. Mitochondria act as a calcium buffer, taking up and releasing intracellular calcium and thus respond to changes in calcium levels by either increasing ATP production or triggering programmed cell death. Mitochondria has a huge role in cell metabolism and cell death and increased calcium accumulation in the mitochondria can trigger the production of reactive oxygen species (ROS).

Calcium Signalling in Nicotinic Acetylcholine Receptors (nAChR)

These receptors are located on cell membranes in the central nervous system and other non-neuronal cells. They activate in response to nicotine and when activated, induces an influx of calcium ions into the cell.

To evaluate the effects of nicotine and e-cigarette exposure on these receptors, the authors used a calcium reporter tagged with GFP and imaged the cells before and after exposure of varying concentrations.

In addition, they wanted to test if blocking calcium could rescue these mitochondrial effects. They blocked calcium influx in 3 different ways:

• blocking the mitochondrial calcium uniporter, a channel that allows a large influx of calcium ions into the cell
• using an antagonist to block the nicotinic acetylcholine receptors on the cell membrane
• chelating extracellular calcium using EGTA