Central Activation of the Cholinergic Anti‐Inflammatory Pathway Improves Outcome in a Murine Model of Systemic Lupus Erythematosus

Abstract

The cholinergic anti‐inflammatory pathway is an endogenous vagus‐to‐spleen mechanism that regulates the immune system and when activated, results in decreases in systemic inflammation. Previous studies from our group demonstrated that the pharmacological potentiation of the efferent vagus nerve via systemic administration of galantamine reduces renal inflammation and blood pressure in systemic lupus erythematosus (SLE), suggesting an impairment in the cholinergic anti‐inflammatory pathway in this model. In this study, we aimed to delineate specific pathways and we hypothesized that central stimulation of vagal efferents by selective activation of neurons within the dorsal motor nucleus of the vagus (DMVN) would similarly protect SLE mice and confirm the role of the cholinergic anti‐inflammatory in controlling inflammation. For that, we selectively activated DMVN neurons using designer receptors exclusively activated by designer drugs (DREADDs). Female NZBWF1 (SLE) and parental control – NZW (Control) mice (n=3‐8) received bilateral microinjections of pAAV‐hSyn‐hM3D(Gq)‐mCherry or pAAV‐hSyn‐mCherry (control virus) into the DMVN at 31 weeks of age. Two weeks post‐microinjection, DREADD agonist CNO (3mg/kg) was administered subcutaneously for 2 weeks starting at 33 weeks. At 35 weeks, mice were housed in metabolic cages for urine collection and catheters were implanted in the carotid to access mean arterial pressure (MAP) in conscious mice. Mice were subsequently euthanized, spleen was collected for Western blotting, blood for double‐stranded (ds) DNA autoantibody quantification and brain to confirm the site of virus microinjection. Selective activation of DMVN neurons did not alter MAP (mmHg) in SLE mice (SLE: 146 ± 6 vs SLE/Gq DREADD: 142 ± 3) or controls (Control: 126 ±4 vs Control/Gq DREADD: 132 ± 2), and also did not change dsDNA autoantibodies (activity units) in SLE mice (SLE: 4.7e5± 1.1e4 vs SLE/Gq DREADD: 3.7e8 ± 1.3e6) or controls (Control: 1.8e5± 5.3e4 vs Control/Gq DREADD: 2.8e5± 1.3e5). Splenic TNFα protein expression was increased in SLE mice compared to controls (SLE: 1.9e6 ± 3.6e5 vs Control: 6.5e5 ± 8.6e4, p=0.001) and DMVN neuron activation decreased splenic TNFα expression in SLE mice (SLE: 1.9e6 ± 3.6e5 vs SLE/Gq DREADD: 1.1e6 ± 1.1e5, p=0.05) but not controls (Control: 6.1e6 ± 3.1e6 vs Control /Gq DREADD: 1.7e6±4.4e5). Albumin excretion rate (µg/day) was higher in SLE mice compared to controls (SLE: 10210±4015 vs Control 97.1±54.3, p=0.07) and DMVN neuron stimulation decreased albumin excretion rate in SLE mice although not significantly (SLE/Gq DREADD: 207.4±142.1, p=0.07). In addition, selective activation of DMV neurons decreased urinary leukocytes (62.5% vs 50%) and blood in the urine (50% vs 16%) in SLE mice. The present study showed that boosting the cholinergic anti‐inflammatory pathway via selective activation of vagal efferents lowered splenic inflammation and protected the kidney without altering blood pressure suggesting an important role of the cholinergic anti‐inflammatory pathway in regulating inflammation and renal injury in SLE.