Oxidative stress - Advantages and disadvantages

Oxidative stress results primarily from an imbalance between molecules potentially dangerous to our cells, the so-called reactive oxygen species, and molecules that protect the oxidative integrity of our cellular structures, as discussed in another post (more information here). When this imbalance favors the former, or disadvantages the latter, we have the condition called oxidative stress.
Oxidative stress is the mainstay of the aging theory, because although we have several antioxidant defenses to protect us, there are always reactive oxygen species that can bypass these defenses, causing little damages that start to accumulate. Furthermore, in the case of smokers, there is permanent oxidative stress, especially at the level of lung cells, since tobacco smoke contains large amounts of reactive oxygen species (and reactive nitrogen species, but I will not talk about them today), which causes the antioxidant defenses in the lungs to be unable to cope completely with the aggressions from tobacco smoke.
But not everything is bad news, because our biochemistry is full of examples where even the most dangerous situations/molecules can be converted into an advantage, at least in some contexts... This is what happens with oxidative stress! Although it is a potentially fatal situation for cells and therefore, most often, is a situation we should avoid, there is a context where oxidative stress is beneficial to our body. I'm talking about the inflammatory response...

In a simple way, when there is an invading microorganism (or other types of stimuli), our organism detects that something is not well, and initiates the inflammatory response. One of the most important cellular components of it is neutrophils, a class of white blood cells. One of the ways neutrophils act, is related to their contact with invading microorganisms. In response to this situation, neutrophils increase their metabolic rate, and the reason is simple: they want to overproduce reactive oxygen species, that means, they want to induce oxidative stress. Of course, this is a controlled process, that is, the stimulation of oxidative stress occurs at a level that can still be effectively eliminated by our antioxidant defenses, but most microorganisms will no longer have this capability. Thus, neutrophils induce oxidative stress, at a level still tolerated by most of our cells, but not tolerated by most microorganisms. In this way, the invasion is controlled and ideally does not cause significant damage to our body.
Therefore, even oxidative stress can be advantageous, as long as properly controlled. It is another notable example of how fascinating is the World of Biochemistry ... ;)