Adrenergic system: A gateway of reciprocal signaling between host and bacteria

The adrenergic system plays a central role in human physiology. However, it can also affect commensal bacteria via adrenergic hormones. Bacteria use adrenergic hormones as xenosiderophore for iron supply, modulators of biofilm formation, quorum-sensing autoinducers regulating virulence factors and pathogenicity, and for interaction with other commensals influencing the microbiome profiles. Bacteria also produce biogenic amines through aromatic amino acid decarboxylation which is widely expressed in human commensals. These biogenic amines are capable of interacting with adrenergic receptors, leading to a variety of different effects on the human body. Phenylacetyl acid is another compound produced by bacteria found in the gut that acts as a precursor of phenylacetylglutamine, a compound that has been linked to cardiac diseases due to its ability to induce thrombosis by activating adrenergic receptors present in platelets.