Nature: Liver-brain-intestinal axis helps maintain immune cells in the gut

The interaction between the intestinal-brain axis, or the central nervous system (CNS) and peripheral intestinal functionsRecent clinical and experimental evidence suggests that interactions between the central nervous system and the gut microbiome are closely related to the bidirectional effects of inflammatory bowel disease (IBDs) and central nervous system diseasesDespite recent advances in our understanding of neural immune interactions, it is not clear how the gut and brain communicate to maintain intestinal immune balance, including the induction and maintenance of peripheral regulatory T cells (pTreg cells), and what environmental cues prompt the host to protect itself from IBDsRecently, researchers have discovered a new liver-brain-intestinal nerve axis that ensures proper differentiation and maintenance of pTreg cells in the gutThe liver's vagus nerve sensations are introduced to be responsible for indirectly sensing the intestinal microenvironment and transferring the sensory input to the binding nucleus of the brain stem, which is eventually transmitted to the vagus parasympathetic nerve and intestinal neuronsSurgery and chemical disturbances inthemion levels of the liver's vagus nerve sensation significantly damage the intestinal pTreg cells because of impaired expression of alaldehyde dehydrogenase (ALDH) and retinal acid (RA) synthesis of intestinal antigen-delivering cells (APCs)The activation of the musk Ach receptor (mAChR) can directly induce alDH gene expression in human and mouse intestinal APCs, while the gene ablation of mAChRs eliminates the excitement of APC in vitroThe destruction of colitis in the model from the liver to the brain stem of the left vagus nerve sensation introduced, reducing the colon pTreg library, resulting in increased susceptibility to colitisThese results suggest that the new vagus neuropathic brain reflex arc can adjust the number of pTreg cells to maintain a steady state of the intestineIntervention sourcing this autonomous feedback feed-forward system can help develop new treatment strategies to treat or prevent immunological diseases in the intestines