The Mast Cell-Aryl Hydrocarbon Receptor Interplay at the Host-Microbe Interface

Abstract

Mast cells are increasingly being recognized as crucial cells in the response of the organism to environmental agents. Interestingly, the ability of mast cells to sense and respond to external cues is modulated by the microenvironment that surrounds mast cells and influences their differentiation. The scenario that is emerging unveils a delicate equilibrium that balances the effector functions of mast cells to guarantee host protection without compromising tissue homeostasis. Among the environmental components able to mold mast cells and fine-tune their effector functions, the microorganisms that colonize the human body, collectively known as microbiome, certainly play a key role. Indeed, microorganisms can regulate not only the survival, recruitment, and maturation of mast cells but also their activity by setting the threshold required for the exploitation of their different effector functions. Herein, we summarize the current knowledge about the mechanisms underlying the ability of the microorganisms to regulate mast cell physiology and discuss potential deviations that result in pathological consequences. We will discuss the pivotal role of the aryl hydrocarbon receptor in sensing the environment and shaping mast cell adaptation at the host-microbe interface.

Silymarin Alleviates Oxidative Stress and Inflammation Induced by UV and Air Pollution in Human Epidermis and Activates β-Endorphin Release through Cannabinoid Receptor Type 2

“…In a first assay, SM was shown to be a weak agonist of human CB2R, similar to CBD. Further tests were conducted on mast cells, which appeared as an appropriate model, as they play a key role in immunity and microbiota management thanks to the AHR [34], in the maintenance of epidermal barrier function [35], and some evidence suggests the role of CB2R in immune modulatory effects during inflammation [50,54]. Very interestingly, SM was found to activate CB2R and induced the release of β-endorphin from mast cells in a similar way as CBD.…”

“…Mast cells are immune cells having an important role in the first-line defense of skin and in the regulation of barrier function [34,35]. They express CB2R, as keratinocytes, and appeared as a good model to test the potential SM agonist's effect [36].…”