Gts-21 Has Cell-Specific Anti-Inflammatory Effects Independent Of Alpha 7 Nicotinic Acetylcholine Receptors

alpha 7 Nicotinic acetylcholine receptors (nAChRs) reportedly reduce inflammation by blocking effects of the important pro-inflammatory transcription factor, nuclear factor kappa-light chain-enhancer of B cells (NF kappa B). The alpha 7 nAChR partial agonist GTS-21 reduces secretion of pro-inflammatory cytokines including interleukin-6 (IL6) and tumor-necrosis factor (TNF) in models of endotoxemia and sepsis, and its anti-inflammatory effects are widely ascribed to alpha 7 nAChR activation. However, mechanistic details of alpha 7 nAChR involvement in GTS-21 effects on inflammatory pathways remain unclear. Here, we investigate how GTS-21 acts in two cell systems including the non-immune rat pituitary cell line GH4C1 expressing an NF kappa B-driven reporter gene and cytokine secretion by ex vivo cu ltures of primary mouse macrophages activated by lipopolysaccharide (LPS). GTS-21 does not change TNF-stimulated NF kappa B signaling in GH4C1 cells expressing rat alpha 7 nAChRs, suggesting that GTS-21 requires additional unidentified factors besides alpha 7 nAChR expression to allow anti-inflammatory effects in these cells. In contrast, GTS-21 dose-dependently suppresses LPSinduced IL6 and TNF secretion in primary mouse macrophages endogenously expressing alpha 7 nAChRs. GTS-21 also blocks TNF-induced phosphorylation of NF kappa B inhibitor alpha (I kappa Ba), an important intermediary in NF kappa B signaling. However, alpha 7 antagonists methyllycaconitine and a-bungarotoxin only partially reverse GTS-21 blockade of IL6 and TNF secretion. Further, GTS-21 significantly inhibited LPS-induced IL6 and TNF secretion in macrophages isolated from knockout mice lacking alpha 7 nAChRs. These data indicate that even though a discrete component of the anti-inflammatory effects of GTS-21 requires expression of alpha 7 nAChRs in macrophages, GTS-21 also has anti-inflammatory effects independent of these receptors depending on the cellular context.