We have previously demonstrated that the pharmacotherapy with donepezil, an acetylcholinesterase inhibitor, suppresses cardiac remodeling in a mouse model of ischemic heart failure after myocardial infarction (MI). However, the precise mechanisms of the cardioprotective effect of donepezil have not been completely delineated. Because post-ischemic inflammation is a pathological key event in the cardiac remodeling process following MI, we investigated the hypothesis that donepezil acts as an inhibitor of inflammatory mediators. RAW 264.7 murine macrophage cells were pretreated with donepezil (100 μM) prior to a pro-inflammatory stimulation by administration of lipopolysaccharide (LPS, 10 ng/ml). Donepezil significantly reduced intra- and extracellular levels of various kinds of inflammatory mediators such as TNF-α, IL-1β, IL-2, IL-6 and IL-18 after the LPS stimulation, and attenuated LPS-induced nuclear translocation of nuclear factor-kappa B (NF-κB). These results indicate that donepezil possesses an anti-inflammatory property. However, the inhibitory effect of donepezil on the macrophage inflammatory responses was never reproduced by ACh, nor was disrupted by ACh receptor blockers. Moreover, other kinds of acetylcholinesterase inhibitors failed to inhibit the inflammatory responses in LPS-stimulated macrophage cells. These results suggest that a cholinergic anti-inflammatory pathway would not be involved in the anti-inflammatory effect of donepezil and that the specific characteristics of donepezil in suppressing the LPS-induced cytokine release and the NF-κB activation would be independent of its acetylcholinesterase inhibition. The present study showed that donepezil exerts an anti-inflammatory effect independently of acetylcholinesterase inhibitory action, thereby donepezil may contribute to cardioprotection during cardiac remodeling process in an ischemic heart failure after MI.Graphical abstract
A schematic drawing of the inflammatory signaling pathway in the LPS-stimulated macrophage showing the point of inhibitory action of donepezil. Activation of TLR4 with LPS initiates a MyD88-dependent cascade that promotes the transcription and production of proinflammatory mediators through the translocation of NF-κB from cytoplasm to nucleus. Donepezil has an ability to attenuate the LPS-induced inflammatory response by inhibiting the nuclear translocation of NF-κB (red solid line). The molecular mechanism of the donepezil-specific anti-inflammatory effect remains unclear. Further studies are needed to clarify the existence of a donepezil receptor (green disc on cell membrane) and a signaling pathway downstream of the receptor.