Molecular mechanisms of α7-nAchR-mediated anti-inflammatory effects

The cholinergic anti-inflammatory pathway is described as an interaction between the nervous system and the immune system. This interaction is regulated by the α7 subtype of cholinergic nicotinic Ach receptors (α7-nAchR), which leads to a marked decrease in the inflammatory cytokines, such as interleukin (IL)-1β, IL-6 and tumour necrosis factor α. Several ligands that interact with α7-nAchR have been recently discovered. These ligands vary in their source, chemical structure, selectivity, potency and efficacy. Activation of α7-nAchR either selectively or non-selectively showed an anti-inflammatory effect that could be due to the inhibition of inflammatory signalling pathways such as Toll-like receptor 4/nuclear factor kappa B inflammasome and mammalian target of rapamycin-mediated autophagy pathways. In addition, it was proved that continuous activation of α7-nAchR could stimulate several anti-inflammatory signalling mechanisms, including Janus activated kinase-2/signal transducer and activator of transcription 3, nuclear factor erythroid 2-related factor 2/HO-1 and adenosine monophosphate-activated protein kinase signalling. In this review, we focused on the recent discoveries of α7-nAchR agonists and antagonists and their anti-inflammatory mechanisms.