Effect of systemic administration of α7-nicotinic acetylcholine receptor ligands on renal inflammation in young mice with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease where renal inflammation contributes to hypertension. The cholinergic anti-inflammatory pathway is a recently described pathway where stimulating the vagus nerve causes release of acetylcholine from choline acetyltransferase (ChAT)+ T-cells in the spleen. This acetylcholine acts on alpha-7 nicotinic acetylcholine receptors (α7nAChR) of immune cells to hault the production of pro-inflammatory cytokines. Our lab has shown stimulation of this pathway at multiple levels lessens autoimmunity, renal inflammation and hypertension in SLE mice. However, our recent attempts to target the α7nAChR directly with a positive allosteric modulator (PAM) in mice with advanced SLE have not yielded similar results. This may be due to decreased parasympathetic tone in these mice in which the PAM is not able to compensate for. The aim of the current study was to determine if activating the α7nAChR in SLE mice at an earlier age, before dampening of parasympathetic tone, prevents the onset of hypertension and renal inflammation. Twelve week old female NZBWF1 mice, which spontaneously develop SLE, and NZW controls were given a partial agonist of the α7nAChR, GTS-21, a PAM, PNU-120596, or vehicle continuously for two weeks via subcutaneous osmotic mini-pump. Mean arterial pressure (MAP) was measured by carotid artery catheter in conscious, freely moving mice at 14 weeks. Mice were then euthanized and blood, spleen and kidneys harvested to allow measurement of plasma double stranded (ds) DNA autoantibodies via ELISA to assess severity of disease. There was no difference in dsDNA autoantibody activity (U/mL) between SLE mice and controls (all data presented as mean±SEM; 76026.3±38901.4 vs. 19617.4±4092.7; p=0.1141). The treatments had no effect on autoantibody activity in SLE mice [76026.3±38901.4 (SLE vehicle) vs. 36951.7±5962.3 (SLE PNU) vs. 56279.7±31381.0 (SLE GTS)] or controls [19617.4±4092.7 (Con vehicle) vs. 17293.2±3384.1 (Con PNU) vs. 16016.2±3059.6 (Con GTS)]. MAP (mmHg) did not differ significantly between young SLE and control mice (143.53±3.26 vs. 128.8±4.95). Additionally, the treatments had no effect on MAP of SLE mice [143.53±3.26 (SLE vehicle) vs. 128.32±10.92 (SLE PNU) vs. 129.56±19.50 (SLE GTS)] or controls [128.8±4.95 (Con vehicle) vs. 127.60±4.43 (Con PNU), vs. 125.65±5.54 (Con GTS)]. Based on these results, we suspect that the disease process has not progressed enough in 14-week-old mice to see differences due to these treatments. Although the changes in the blood pressure and dsDNA antibodies are not significant, we will continue to evaluate renal damage and cytokine profile to determine the effect of these α7nAChR ligands on pathogenesis of SLE. Future studies will aim to modulate α7nAChRs in SLE mice before the onset of disease (~12 weeks of age) through 35 weeks when mice usually experience terminal disease to determine efficacy of early activation of the cholinergic anti-inflammatory pathway in halting the progression of SLE.