The body's own cannabinoid system helps regulate immune tolerance in the gut and pancreas | Research

The takeaway

Anandamide, the body's natural cannabinoid, promotes immune tolerance in the gut through CB2 receptors, and capsaicin (from hot peppers) triggers the same pathway, protecting mice from type 1 diabetes.

Read this if you're curious about how the endocannabinoid system connects the gut, the immune system, and the nervous system.

Oral anandamide protected mice from type 1 diabetes by promoting gut immune tolerance

What the researchers found

The endocannabinoid anandamide (AEA) and its receptor CB2 regulate immune tolerance in the gut and pancreas. Anandamide increased the number and suppressive function of regulatory CX3CR1-high macrophages in the gut, which expressed the highest levels of cannabinoid receptors among gut immune cells.

Capsaicin, the compound that makes peppers hot, triggered the same pathway indirectly: it activated TRPV1 receptors, which caused local production of anandamide, which then acted through CB2. This also promoted differentiation of regulatory T cells (Tr1 cells) through an IL-27-dependent mechanism.

In a functional test, the immune tolerance created by this pathway could be transferred to other mice through CD4+ T cells. Oral administration of anandamide protected NOD mice (a model for type 1 diabetes) from developing the disease.

Why it matters

This study reveals a previously unknown conversation between the nervous system and immune system in the gut, mediated by endocannabinoids. The finding that this pathway can be activated by capsaicin (a dietary compound) to prevent autoimmune diabetes opens possibilities for both understanding and treating autoimmune conditions.

The numbers in context

TRPV1 knockout and CB2 knockout mice had fewer CX3CR1-high regulatory macrophages in the gut. Oral anandamide administration protected NOD mice from developing type 1 diabetes. Immune tolerance was transferable via CD4+ T cells.

How the study worked

The study used multiple mouse models including TRPV1 knockout and CB2 knockout mice, along with the NOD mouse model of type 1 diabetes. Researchers used flow cytometry, cell transfer experiments, and in vitro differentiation assays to map the signaling pathway from capsaicin/TRPV1 through anandamide/CB2 to immune regulatory cells.

What this study cannot tell us

All findings are from mouse models and may not directly translate to human biology. The NOD mouse is an imperfect model of human type 1 diabetes. Oral anandamide dosing in mice differs significantly from what would be feasible in humans. The study does not address whether exogenous cannabinoids (like THC) would produce similar effects.

How to read the evidence

Animal study published in PNAS using multiple mouse models and sophisticated immunological techniques. Strong mechanistic evidence in animals but not yet tested in humans.

When this study was published

Published in 2017. The role of endocannabinoids in gut immune regulation has continued to attract research attention.

The bigger picture

The gut's endocannabinoid system appears to serve as a bridge between the nervous and immune systems, actively maintaining the balance between immune vigilance and tolerance. This has implications far beyond cannabis, suggesting that the endocannabinoid system is a fundamental regulator of immune homeostasis, and that dietary compounds like capsaicin can tap into this system.

Questions still open

Could targeting the gut endocannabinoid system prevent or treat autoimmune diseases in humans? Does regular capsaicin consumption actually affect immune tolerance through this pathway? Would THC or CBD activate similar gut immune regulatory mechanisms?

Common questions

Does eating spicy food boost your immune system through cannabinoids?

The study found that capsaicin triggered anandamide production in the gut, which promoted immune regulatory cells. However, this was demonstrated in mice with controlled dosing. Whether regular dietary capsaicin intake in humans produces meaningful immune effects through this pathway is unknown.

Could cannabis affect gut immunity?

This study focused on anandamide (the body's own cannabinoid) rather than plant cannabinoids like THC. While THC also acts on cannabinoid receptors, whether it would activate the same gut immune tolerance pathway is unclear and was not tested.

Read the original research

Endocannabinoid system acts as a regulator of immune homeostasis in the gut.

Proceedings of the National Academy of Sciences of the United States of America, 114(19), 5005-5010

View on PubMed ↗Publisher’s paper ↗

Citation

Acharya, Nandini; Penukonda, Sasi; Shcheglova, Tatiana; Hagymasi, Adam T; Basu, Sreyashi; Srivastava, Pramod K. (2017). Endocannabinoid system acts as a regulator of immune homeostasis in the gut.. Proceedings of the National Academy of Sciences of the United States of America, 114(19), 5005-5010. https://doi.org/10.1073/pnas.1612177114