We all know we acquire grey hair, declining senses and feel our body changing as we age, but how do our cells—those microscopic components that make up our body—change as we grow old? Biologists have known the answer for most cells in our bodies. As cells age, their DNA gets accumulatively damaged over time, and this DNA damage leads to a ‘senescence pathway’ via a DNA damage response (DDR). This DDR permanently arrests any further division of the cell and leads to changes in the expression of many genes (including many inflammatory genes) and also leads to dysfunction of the cell’s respiratory machine, the mitochondria. It doesn’t stop here. The DDR induces the damaged cell to release a host of toxic ‘reactive oxidative species’, which then affect the entire tissue.
However, this sequence of events has only been observed in cells that have the ability to divide—a category that includes most cells in the body, but leaves out the cells of the brain, the neurons. Researchers at Newcastle university have recently studied brain cells of mice to study how they age, and they have found the same senescence pathway active in the aging brain. To study this, they isolated cells from various brain regions of mice and looked for the presence of ‘molecular markers’—in this case, molecules that would indicate that a certain pathway or gene was activated. For instance, Interleukin-6 was a protein molecule that was used as a molecular marker for the inflammation found in aging cells. Using many such markers, they found that the exact senescence pathway previously found in dividing cells was also active in neurons.
Until now, it was assumed that aging pathways in the brain would be different, but this research shows that this is not the case. Using this information about aging neurons gives us an avenue to better understand the mechanisms of age-related mental disorders such as cognitive decline.
You can read about this research here.