Our bodies harbor cells that have stopped dividing but haven't died. Think of them as old workers who no longer show up for their shift but still take up space and get in the way of the young ones. These cells release harmful substances and accelerate aging. Scientists want to remove them without harming healthy cells.
It turns out you can do this with the antioxidant N-acetylcysteine, but only at a very high dose. In the lab, researchers grew human muscle cells and aged them. Then they added the antioxidant at a concentration of 20 millimoles. The senescent cells began to die off, while normal cells were barely affected. It's like putting an extra little weight on one pan of a scale that was already teetering on the edge of balance.
People used to think antioxidants always protect cells. Now it's clear that everything depends on the dose. A low dose offers mild protection, while a high dose kills specifically the senescent cells. This discovery points the way toward anti-aging drugs, but so far no practical applications are in sight: the dose required is too large for a human.
N-acetylcysteine is often sold as a dietary supplement to support the liver and lungs. In this work, it was used at concentrations tens of times higher than those reached in the blood after taking the supplement.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.