Vagus nerve cholinergic circuitry to the liver and the gastrointestinal tract in the neuroimmune communicatome

Improved understanding of neuroimmune communication and the neural regulation of immunity and inflammation has recently led to proposing the concept of the "neuroimmune communicatome." This advance is based on experimental evidence for an organized and brain-integrated reflex-like relationship and dialogue between the nervous and the immune systems. A key circuitry in this communicatome is provided by efferent vagus nerve fibers and cholinergic signaling. Inflammation and metabolic alterations coexist in many disorders affecting the liver and the gastrointestinal (GI) tract, including obesity, metabolic syndrome, fatty liver disease, liver injury, and liver failure, as well as inflammatory bowel disease. Here, we outline mechanistic insights regarding the role of the vagus nerve and cholinergic signaling in the regulation of inflammation linked to metabolic derangements and the pathogenesis of these disorders in preclinical settings. Recent clinical advances using this knowledge in novel therapeutic neuromodulatory approaches within the field of bioelectronic medicine are also briefly summarized.