Oxidative Stress May Have Little Effect On Lifespan

Cell sensitivity to oxygen exposure and oxidative stress doesn’t correlate with lifespan

The free radical theory is one of the oldest theories of why we age, but research has proved oxidative stress plays a far subtler role in aging than first believed, and may be a relatively minimal factor, 

Most of your cells survive on a fairly low oxygen concentration, and very few are actually exposed to the surrounding air directly. This has made cell culturing complicated, as exposing cell types to an uncontrolled air supply produces an environment different to their natural habitat – making many experimental findings difficult to apply to in vivo (inside the body) processes. 

How important is oxidative stress?

In a new study seeking to compare oxygen sensitivity to lifespan, lung and skin cells from 16 rodent species were cultured in 2 different concentrations of oxygen: 3 or 21%. Their growth rate and division was then measured and compared. 

Credit: Smithsonian’s National Zoo

The cells from laboratory mice are notoriously sensitive to oxygen, but other species like the naked mole rat and hamster demonstrated mild sensitivity to oxygen levels. Others such as deermouse and guinea pig cells were unaffected by oxygen increases. Increased oxygen levels increases oxidative reaction in the cell – producing higher levels of reactive molecules. 

The researchers made a surprising discovery

Although some species’ cells were hardier and more resistant to high levels of oxygen, the rodent species with greater sensitivity were paradoxically longer lived. Even though their cells in the laboratory environment were more sensitive, this didn’t seem to impact on their longevity. The naked mole rat in particular lives 31 years, which is quite astonishing for a rodent. This means that oxidative stress likely plays a very minimal role in the aging process when it comes to rodents, if at all. 

“Our findings open up many areas to explore in the field of aging and regenerative medicine. With these new insights it would be very interesting to know whether non-rodent large mammals of veterinary interest including cats, dogs and horses would have the same reaction to oxygen to that found in rodents. Nowadays people regard antioxidants as the so-called ‘elixir of life’, however, our results cast doubt on this claim at least for some rodents, with mice being an exception”

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