Tuesday, September 22, 2009

A Little Stress Goes a Long Way: 26 weeks of anti-tumour activity

Short Term Stress Enhances Anti-tumor Activity In Mice, Study Shows.


Researchers at the Stanford University School of Medicine have shown that, at least in laboratory mice, bouts of relatively short-term stress can boost the immune system and protect against one type of cancer. Furthermore, the beneficial effects of this occasional angst seem to last for weeks after the stressful situation has ended.


The abstract for the research piece can be downloaded here.

The results of the above study remind of a wonderful review by Sapolsky et al wherein they put forward a model addressing such issues. That was in the days when I was stupid enough to believe I might learn something about what the hell is going on around me. The logic is simple, we don't have to go to acronym city.

The review is somewhat dated now but can be downloaded here:

Stress of just about any kind will activate the stress response axis in our brains. This will induce the release of Corticotrophin Releasing Factor, a hormone that stimulates the adrenal glands to start pumping out cortisol and other stress hormones. Corticotrophin Releasing Factor is released at the base of the brain and must travel via the bloodstream to the adrenal glands which sit on top of our kidneys. This hormone not only stimulates the adrenal glands to pump out immune dampening cortisol it also activates a variety of immunological cells and will promote inflammation until such time as cortisol levels rise to dampen the response. Whereas inflammatory mediators are stored in various cells and can be immediately released through the appropriate signals, it can take several hours for cortisol levels to reach sufficiently high levels to dampen the immunological activation.

Therein lies the beauty of this evolutionary strategy because stress implies injury so you want the immune system primed to address injuries. It is important to remember that the "immune system" and "inflammation" play essential roles in healing, nutrient provision, and growth factors to injured tissues. If there is an injury a great many inflammatory mediators will be released at the site of injury. So even by the time cortisol comes into play, this region will be loaded up with immunological warriors and repair crews while the inflammatory response in the rest of the body is being suppressed by the cortisol. If there is no injury, things settle back to the forever wavering physiological changes that make a mockery of "homeostasis".

So short term stress has the benefit of occasionally raising the alert status of the immune system, thereby enabling it to identify and target pre cancerous and cancerous cells. This touches on something I have often wondered about: it may be a good idea not to try and fixate a physiological state because most such states have upsides.

As to the sustained effects of the response, I can make no theoretical sense of that which means it is time to get off my lazy arse and start learning again(Ha!). I suspect the cause of the sustained response is that every time the researchers approached the cages to take more blood samples the mice looked up and thought, "SHIT, here we go again." After six months they got used to it.

1 comment:

Francis Xavier Holden said...

john - I have no references but I was told by a respected researcher that most ( a big most) don't keep mice/rats alive long enough to really study ageing effects.

They can statistically extrapolate out but the ageing process itself isn't linear or always predictable in its physical effects and much is being missed by using rodents for less time.

This has to do with the costs of keeping mice /rats in labs long enough. Thee is a small trend by some labs to keep mice/rats a lot ( I think twice as long from memory) in order to do much better science.

This is of particular concern in drug tests and anti aging stuff and also dementia research.

You might be able to dig up some info on the length of time that ideally should be used in mice /rats for studies related to human ageing