miR-132 inhibits lipopolysaccharide-induced inflammation in alveolar macrophages by the cholinergic anti-inflammatory pathway

Objective: Although microRNA-132 (miR-132) has been shown to be involved in the inflammatory regulation, its role in sepsis-induced lung injury is unknown. We hypothesized that miR-132 attenuated lipopolysaccharide (LPS)-induced inflammation of alveolar macrophages by targeting acetylcholinesterase (AChE) and enhancing the acetylcholine (ACh)-mediated cholinergic anti-inflammatory response. Methods: The LPS-treated rat alveolar macrophage cell line NR8383 was used as the inflammatory model. To assess the effect of miR-132, alveolar macrophages were transfected with nniR-132 mimic or inhibitor. Results: We found that nniR-132 was upregulated in LPS-stimulated alveolar macrophages. Induction of AChE mRNA showed an inverse pattern with respect to AChE protein and activity, suggesting posttranscriptional regulation of AChE. Utilizing miR-132 mimic transfection, we found that overexpression of miR-132 enhanced the ACh-mediated cholinergic anti-inflammatory reaction by targeting AChE mRNA in LPS-treated alveolar macrophages. Blockage of miR-132 using miR-132 inhibitor reversed the Ach action upon LPS-induced release of inflammatory mediators and reduction in AchE protein/activity. Moreover, in the presence of ACh, upregulation of miR-132 suppressed LPS-induced nuclear translocation of NF-kappa B and production of STAT3 and phosphorylated STAT3, while downregulation of miR-132 enhanced the nuclear translocation of NF-kappa B. Conclusion: We propose that miR-132 functions as a negative regulator of the inflammatory response in alveolar macrophages by potentiating the cholinergic anti-inflammatory pathway, and represents a potential therapeutic leverage point in modulating inflammatory responses.