Today, I want to talk about the autonomic nervous system (ANS) and the large role it plays in managing both inflammation and the immune system. This may be interesting to people living with autoimmune, immune-mediated, and inflammatory conditions.

The sympathetic and parasympathetic nervous systems are two branches of the autonomic nervous system, which regulates involuntary functions like heart rate, digestion, and respiration. You might have heard of the sympathetic nervous system referred to as “Fight or Flight”, and the parasympathetic nervous system referred to as “Rest and Digest”.

It’s pretty complicated with loads of different pathways involved, so let’s break down how the sympathetic and parasympathetic branches work together in these processes.

Sympathetic nervous system (SNS) and inflammation

Pro-inflammatory role: The sympathetic nervous system can act in two ways when it comes to inflammation, but when you’re dealing with something like stress from an injury or infection, it usually cranks up the inflammation. This happens because norepinephrine (that’s adrenaline) is released from sympathetic nerves and adrenal glands, which:

• Boosts the production of pro-inflammatory cytokines like TNF-α, IL-1, and IL-6, which promote inflammation.
• Give immune cells like macrophages a nudge to jump into action and tackle infections or any tissue damage.

Chronic stress and immune suppression: When your stress levels are high for a long time, it messes with your immune system. This means your body struggles to fight off infections and heal tissue etc. Long-term sympathetic activation can dysregulate inflammation, leading to persistent low-grade inflammation. This is linked to conditions such as autoimmune diseases, cardiovascular issues, and chronic inflammatory diseases.

Parasympathetic nervous system (PNS) and the “Anti-Inflammatory Reflex”

Anti-inflammatory role: The parasympathetic nervous system, specifically through the vagus nerve, plays a crucial role in reducing inflammation. This is often referred to as the “cholinergic anti-inflammatory pathway”, where:

• The vagus nerve releases acetylcholine, which binds to immune cells like macrophages and helps tone down the production of those pesky pro-inflammatory cytokines.
• This reduces systemic inflammation and prevents excessive immune responses.

This anti-inflammatory reflex helps maintain immune balance and prevents damage from overactive immune responses. It’s part of why vagus nerve stimulation or activities that stimulate the parasympathetic system (like breathing exercises) can help reduce inflammation and pain in conditions like rheumatoid arthritis, inflammatory bowel disease (IBD), and other chronic inflammatory conditions.

Autonomic nervous system and immune system modulation

The ANS interacts closely with the immune system. Both sympathetic and parasympathetic pathways can influence immune cells such as T cells, macrophages, and dendritic cells.

• The sympathetic nervous system generally promotes an initial immune response to infection, but prolonged activation can suppress it, leading to immune dysregulation.
• The parasympathetic nervous system, on the other hand, helps return the body to a baseline state, preventing overactivation of immune responses and reducing chronic inflammation.

Clinical implications:

Chronic inflammatory diseases: Dysregulation of the autonomic nervous system is linked to diseases like rheumatoid arthritis, IBD, and fibromyalgia, where the balance between inflammation and anti-inflammation is disturbed.

Vagus nerve stimulation: Research shows that stimulating the vagus nerve (either through medical devices or techniques like deep breathing) can reduce inflammation in people with chronic conditions.

Conclusion

The autonomic nervous system plays a significant role in both promoting and controlling inflammation and immune responses, depending on the context (short term vs. chronic stress) and which part of the system (sympathetic nervous system vs. parasympathetic nervous system) is activated.

Balancing these systems, especially through techniques that stimulate the parasympathetic system, can help manage inflammation and immune-related disorders.