Abstract
The cholinergic anti-inflammatory pathway (CAP) links the nervous and immune systems and modulates innate and adaptive immunity. Activation of the CAP by vagus nerve stimulation exerts protective effects in a wide variety of clinical disorders including rheumatoid arthritis and Crohn's disease, and in murine models of acute kidney injury including ischemia/reperfusion injury (IRI). The canonical CAP pathway involves activation of splenic alpha7-nicotinic acetylcholine receptor (α7nAChR)-positive macrophages by splenic β2-adrenergic receptor-positive CD4+ T cells. Here we demonstrate that ultrasound or vagus nerve stimulation also activated α7nAChR-positive peritoneal macrophages, and that adoptive transfer of these activated peritoneal macrophages reduced IRI in recipient mice. The protective effect required α7nAChR, and did not occur in splenectomized mice or in mice lacking T and B cells, suggesting a bidirectional interaction between α7nAChR-positive peritoneal macrophages and other immune cells including β2-adrenergic receptor-positive CD4+ T cells. We also found that expression of hairy and enhancer of split-1 (Hes1), a basic helix-loop-helix DNA-binding protein, is induced in peritoneal macrophages by ultrasound or vagus nerve stimulation. Adoptive transfer of Hes1-overexpressing peritoneal macrophages reduced kidney IRI. Our data suggest that Hes1 is downstream of α7nAChR and is important to fully activate the CAP. Taken together, these results suggest that peritoneal macrophages play a previously unrecognized role in mediating the protective effect of CAP activation in kidney injury, and that Hes1 is a new candidate pharmacological target to activate the CAP.