Gut Feeling: MicroRNA Discriminators of the Intestinal TLR9-cholinergic Links

The intestinal tissue notably responds to stressful, cholinergic and innate immune signals by microRNA (miRNA) changes, but whether and how those miRNA regulators modify the intestinal cholinergic and innate immune pathways remained unexplored. Here, we report changes in several miRNA regulators of cholinesterases (ChEs) and correspondingly modified ChE activities in intestine, splenocytes and the circulation of mice exposed to both stress and canonical or alternative Toll-Like Receptor 9 (TLR9) oligonucleotide (ODN) aptamer activators or blockers. Stressful intraperitoneal injection of saline, the anti-inflammatory TLR9 agonist mEN101 aptamer or the inflammation-activating TLR9 aptamer ODN 1826 all increased the expression of the acetylcholinesterase (AChE)-targeting miR-132. In comparison, mEN101 but neither ODN 1826 nor saline injections elevated intestinal miR-129-5p, miR-186 and miR-200c, all predicted to target both AChE and the homologous enzyme butyrylcholinesterase (BChE). In cultured immune cells, BL-7040, the human counterpart of mEN101, reduced AChE activity reflecting inflammatory reactions in a manner preventable by the TLR9 blocking ODN 2088. Furthermore, the anti-inflammatory BL-7040 TLR9 aptamer caused reduction in nitric oxide and AChE activity in both murine splenocytes and human mononuclear cells at molar concentrations four orders of magnitude lower than ODN 1826. Our findings demonstrate differential reaction of cholinesterase-targeting miRNAs to distinct TLR9 challenges, indicating upstream miRNA co-regulation of the intestinal alternative NFκB pathway and cholinergic signaling. TLR9 aptamers may hence potentiate miRNA regulation that enhances cholinergic signaling and the resolution of inflammation, which opens new venues for manipulating bowel diseases.