Monocytes primed with GTS-21/α7 nAChR (nicotinic acetylcholine receptor) agonist develop anti-inflammatory memory

Background: The neural system can finely tune immune system, especially pro- or anti-inflammatory responses of monocytes/macrophages. To maintain immune homeostasis, monocytes/macrophages are supposed to be primed by alpha 7 nAChR agonist to establish anti-inflammatory memory. Aim: To study whether activation of alpha 7 nAChR would elicit anti-inflammatory memory in splenic monocytes in vivo and J774 monocytes in vitro. Design: Laboratory study. Methods: The wildtype mice were sacrificed 4 or 12 h after receiving intravenous injection of GTS-21. The splenocytes were isolated and stimulated with LPS for 4 h to detect Ly6C(hi) TNF-alpha(+) monocytes by flow cytometry. In the in vitro study, J774 monocytes received priming with GTS-21, washing GTS-21 out and resting, and thereafter stimulating with TLR ligands. The TNF-alpha protein and Tnf alpha, Il1 beta and il6 mRNAs were measured to evaluate anti-inflammatory responses. The H3K9ac, H4K5ac, H4K8ac, Acetyl-CBP, CBP (CREB-binding protein), PCAF (P300/CBP-associated factor) and Acetyl-NF-kB levels were measured in GTS-21-primed monocytes. Results: Activation of alpha 7 nAChR by GTS-21 suppressed TNF-alpha production in splenic Ly6C(hi) monocytes. In vivo-GTS-21-primed splenic Ly6C(hi) monocytes passed on anti-inflammatory feature if stimulated with LPS in vitro. J774 monocytes primed with GTS-21 developed anti-inflammatory trait in response to LPS (TLR4), Poly:IC (TLR3) and R848 (TLR7/8) ligands. In GTS-21-primed monocytes, H3K9ac, H4K5ac, H4K8ac, Acetyl-CBP, CBP, PCAF and Acetyl-NF-kB were reduced 4 h after washing and resting. In the nuclear extract, PCAF, Acetyl-NF-kB, p-NF-kB and p-STAT3 were decreased in LPS-stimulated GTS-21 primed J774 monocytes 4 h after washing and resting. Conclusions: Monocytes primed by alpha 7 nAChR agonist developed anti-inflammatory memory.