The brain as a regulator of inflammation
In recent years we have become aware that, from an evolutionary, biological and even anthropological point of view, the two priority systems for the survival of the human being (and, therefore, the two systems to be prioritized energy supply) are the brain and the immune system.
To understand this is to understand ourselves better.
It doesn’t matter what situation we find ourselves in. Cold, heat, hunger, darkness, pain, fatigue… The response to any bodily state will depend both on the interpretation that the immune system makes of it and on the behavior that the brain decides is optimal for survival.
1. 1. The immune system interprets, discriminates and reacts
The resting immune system is not inactive. It fulfills important bodily functions, such as modulating cell growth. Also support cell cleaning processes or repair damaged tissues.
But, in addition, to be effective you must be able to interpret the changes in the world around you. The immune system must be able to adequately answer this question: do I know this stranger? That is to say: an effective immune system must be able to discriminate. Discriminate what puts our survival at risk from what does not pose a danger.
Indeed, the immune system has an uneasy relationship with the environment. We are constantly facing new situations and, in most cases, this encounter with something new does not pose a threat. Now, on those rare occasions when it isn’t, it can be very dangerous. And an effective immune system must be able to discriminate those differences:
You must distinguish what is your own from what is foreign.
It must distinguish harmless non-self from dangerous non-self.
And, in the face of an alert signal, of danger, it must activate its mechanisms to prioritize obtaining energy.
2. 2. The brain in the face of uncertainty
For its part, when faced with the perception of a threat due to changes in the environment (both external and internal), the brain must answer this question: ‘What behavior should I select to protect my future physical, mental and social well-being?’ That is, you must select a strategy and carry it out. The thing is, you don’t always know what the right strategy is for that situation. In these cases, stress appears and, with it, a greater energy demand by the brain. If the answer is not assured, a feeling of lack of control and uncertainty arises.
It is important to emphasize the concept of uncertainty. Beyond danger, it seems to be the key factor that triggers a stress response, as we see in this study. Uncomfortable, the brain will activate its own mechanisms to capture extra energy. The goal is to learn more about this new situation. And so, find the right strategy.
How does the immune system influence the brain?
Once he recognizes a danger (especially if it’s his first contact with it), he activates his entire arsenal. It produces substances that will make it easier for an extra supply of energy to arrive. At the same time, it ‘seduces’ the brain into generating energy-saving behavior. It is what we know as ‘illness behavior’: we get sick.
This ‘getting sick’ is a coordinated set of adaptive behavioral changes that develop in sick individuals during the course of an infection. Lethargy, depression, drowsiness, malaise, loss of appetite, social withdrawal, lack of concentration… If you realize, the immune system is conditioning behavior and adjusting the expression of neurotransmitters such as dopamine, norepinephrine and serotonin.
And you may be wondering if, in the same way that the immune system generates changes in the brain, the reverse cannot occur. In other words, the brain also promotes changes in the immune response. The answer is: of course it is.
The case of Wim Hoff
To approach this question, I will tell you about an amazing and extreme case. This is the story of Wim Hof. A media personality who has several world records for tolerance to extreme cold to his credit. Hof claims that simply by concentrating, he can influence his autonomic nervous system and thus his innate immune response.
Half-naked Wim Hof meditating on a block of ice
And he not only assures it, but he has lent himself to be the subject of studies to prove it. Thus, while he begins to meditate, 2ng/kg of lipopolysaccharides are introduced to him to simulate endotoxemia. And he compares his response to that of 112 other individuals who have also undergone this same method of inducing endotoxemia. In these other participants, the usual response was 48 hours of immune overactivity. In addition, fever, fatigue and vomiting. Instead, Wim Hof neutralizes the clinic in a quarter of an hour. Furthermore, these results are corroborated by a marked decrease in inflammatory cytokines (immune messengers).
How does the brain influence the immune system?
He began this post by saying that the brain is a priority organ for survival. He is our conductor and, as such, he needs the body to obey, to abide by the decisions he makes. To do this, it has a much more direct and immediate communication system than the rest of the systems. We talk about nerves.
Nerves are transmitters of signals with a unique ability: unlike endocrine factors (such as hormones), they instantly deliver precisely targeted signals
The central nervous system (CNS) communicates with virtually every part of the body through sensory and motor neurons. And, currently, we are beginning to have enough evidence to affirm that the immune system is regulated in a similar way through what has been called the inflammatory reflex.
Control of inflammation mediated by the vagus nerve:
One of the most studied pathways for controlling inflammation through the nerve is the one mediated by the vagus nerve. Studies have shown that activation of efferent vagus cholinergic signaling has profound effects on systemic production of inflammatory markers in endotoxemia (remember Wim Hoff and his voluntary endotoxemia?)
Both pharmacological and electrical stimulation of the vagus nerve reduce levels of proinflammatory cytokines in a wide range of diseases. In contrast, ablation of the cervical vagus nerve avoids these effects (study, study)
Since the vagus nerve winds and branches into a multitude of tissues and organs, it is likely that some of these neural connections are part of neuroimmune reflex circuits other than the prototypical inflammatory reflex.
In addition to the vagus nerve, numerous studies carried out both in vitro and in vivo have shown that catecholamines released by sympathetic nerve fibers also have potent modulatory effects on immune cells. Both in the type of response and in the alteration of the traffic of monocytes and lymphocytes.
In addition to catecholamines, glucocorticoids also have profound effects on immune activity, both activating and suppressing it.
Regardless of the immune system’s interpretation of the environment, the brain is capable of amplifying or modulating the immune response.
In patients in whom immune activity is perpetuated and ceases to be beneficial to the individual, resorting to the “central computer” can give us direct tools for modulating symptoms.
In addition to identifying the causes of the chronic activation of the immune system, helping the person to reduce uncertainty allows the brain to identify that the immune signals are not really so alarming and thus activate its modulation mechanisms.
In turn, the development of new pathways to stimulate the vagus nerve and the different neuroimmunomodulatory actions, although still in the initial phases of study, offers a wide field of approach for therapists. As well as hope for people with immune or autoimmune pathologies.