April 07, 2007
Mycobacterial Vaccination Against Depression?

Vaccination of mice with Mycobacterium vaccae (M. vaccae) boosts their mood.

Treatment of mice with a ‘friendly’ bacteria, normally found in the soil, altered their behavior in a way similar to that produced by antidepressant drugs, reports research published in the latest issue of Neuroscience.

These findings, identified by researchers at the University of Bristol and colleagues at University College London, aid the understanding of why an imbalance in the immune system leaves some individuals vulnerable to mood disorders like depression.

Dr Chris Lowry, lead author on the paper from Bristol University, said: "These studies help us understand how the body communicates with the brain and why a healthy immune system is important for maintaining mental health. They also leave us wondering if we shouldn’t all be spending more time playing in the dirt."

This discovery was an accident. Dr. Lowry was experimenting with the use of M. vaccae to treat lung cancer and found that the mood and cognitive function of lung cancer patients were also boosted by the M. vaccae vaccination.

Interest in the project arose after human cancer patients being treated with the bacteria Mycobacterium vaccae unexpectedly reported increases in their quality of life. Lowry and his colleagues reasoned that this effect could be caused by activation of neurons in the brain that contained serotonin.

When the team looked closely at the brains of mice, they found that treatment with M. vaccae activated a group of neurons that produce the brain chemical serotonin. The lack of serotonin in the brain is thought to cause depression in people, thus M. vaccae’s effects on the behavior of mice may be due to increasing the release of serotonin in parts of the brain that regulate mood.

Vaccination of mice with M. vaccae boosts immune system cytokines and the mice acted less stressed.

As expected, cytokine levels rose. They then looked directly in their animals' brains for the effect of those cytokines.

Cytokines actually act on sensory nerves that run to the brain from organs such as the heart and the lungs. That action stimulates a brain structure called the dorsal raphe nucleus. It was this nucleus that Dr Lowry focused on. He found a group of cells within it that connect directly to the limbic system, the brain's emotion-generating area. These cells release serotonin into the limbic system in response to sensory-nerve stimulation.

The consequence of that release is stress-free mice. Dr Lowry was able to measure their stress by dropping them into a tiny swimming pool. Previous research has shown that unstressed mice enjoy swimming, while stressed ones do not. His mice swam around enthusiastically.

It is worth noting that this work fits in a larger context: the argument (known as the hygiene hypothesis) that humans are suffering more auto-immune diseases such as allergies and asthma due to a lack of exposure to bacteria, digestive tract worms (which might be key to prevention and treatment of inflammatory bowel disease- also see here), and other pathogens. According to this theory people living in modern clean industrialized societies with purified water, refrigerators, automated farms, flush toilets, warm showers, and hand soap the immune system doesn't get exposed to pathogens it is designed to handle. The immune system is designed to work properly only in the presence of those pathogens. So it goes awry and starts attacking things it ought not attack. Considerable amounts of evidence (see here and here) supports the idea that getting dirty might be good for you.

This latest result suggests that other functions of the immune system (e.g. interactions with the nervous system) aren't getting sufficiently stimulated in modern society. So maybe we are suffering from an epidemic of depression (and other mental illnesses while we are at it?) due to excessive purity of our environments. Well, I'm sure glad as a kid that I liked to go out in the yard and build dirt castles and mud walls. City kids didn't have that advantage.

What I'd like to know: Do kids with dogs have a lower risk of getting depressed when they grow up? Do kids who grow up on pig and cow farms similarly have lower risks of adult depression? Also, does depression vary by country due to different vaccination regimes used in different countries?

The larger lesson: We are not in our ancestral environments which we are genetically adapted to. So all bets are off. We need to develop technologies that adapt us to our new environments. Speaking of which: In addition to vaccinations that give our immune systems needed exercise we also need to reshape our work environments to give ourselves more exercise in cubicle land. My suggestion: move exercise bicycles and steppers into meeting rooms and training rooms so that we can get exercise while getting training and giving project status reports.

Share |      Randall Parker, 2007 April 07 09:09 AM  Brain Depression


Comments
rsilvetz said at April 7, 2007 3:12 PM:

Quote: It is worth noting that this work fits in a larger context: the argument (known as the hygiene hypothesis) that humans are suffering more auto-immune diseases such as allergies and asthma due to a lack of exposure to bacteria, digestive tract worms (which might be key to prevention and treatment of inflammatory bowel disease- also see here), and other pathogens. According to this theory people living in modern clean industrialized societies with purified water, refrigerators, automated farms, flush toilets, warm showers, and hand soap the immune system doesn't get exposed to pathogens it is designed to handle. The immune system is designed to work properly only in the presence of those pathogens. So it goes awry and starts attacking things it ought not attack. Considerable amounts of evidence (see here and here) supports the idea that getting dirty might be good for you.

First the industry keeps forgetting that the immune system is a chaotic dynamic system. It depends which attractor you are living in. So it's really useless to say wild rats behave properly and lab rats don't, especially without knowing the shape of the attractors in the dynamic system. It's the wrong question. The lab rats are in a different attractor, and on their most probable diet, in a persistent state of inflammation, that prolongs any stimulus they are hit with. No wonder they get autoimmune disorders. So the lab rats behaved properly as well.

And no -- for correctness -- the immune system does not go awry and attack things. It's working as designed. What happens is that most Western diets are inflammatory and folks are thereby locked in the depths of a persistently activated attractor. Daily living will occasionally damage cells, and the persistently activated T-cells will go on to think the system is under assault when in fact it isn't.

Furthermore, the industry drops the even larger context when they say these things. They forget we dropped dead at ridiculous rates prior to the public health, the economic advances, that removed us from the pathogens. [In context, what is the death rate of the wild rats...?] Few realize that TB was obliterated by improvements in quality of life and not by drugs. The TB rate had been dropping for decades by the time effective treatment removed the remaining clusters. In fact, all infectious diseases were...

What's really happening when you go play in the dirt is that you are excerisizing the system, and when driving it thru the full cycle, you can jump attractors and retire persistently activated T-cells. Further proof of this reality is the elderly that has a septic episode only to find their arthritis gone for years. Even further proof of this is fact that most folks get either cardiovascular disease or cancer, but rarely both. Sitting at the bottom of different attractors, they present with different diseases.

As far as pets in the house, their is generally more disease, not less, but the research is hardly conclusive. Nobody adjusted for hours played in the dirt vs just having the pet.

Hope this helps the discussion.

morpheus said at April 7, 2007 10:02 PM:

yeah i think this was on bbc news

about the happy ass a pig

couse they like dirt, soo makes them happy

did u know the the pig is the most inteligent animal? after the dophins?

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