Potentiation of Acetylcholine Does Not Improve Renal Inflammation and Behavior in Female Mice with Late‐Stage Systemic Lupus Erythematosus

Abstract

Chronic inflammation contributes to the morbidity and mortality in advanced systemic lupus erythematosus (SLE). Endogenous neuroimmune mechanisms like the cholinergic anti-inflammatory pathway can be targeted to modulate inflammation, but the ability to manipulate such pathways and reduce inflammation and end organ damage has not been fully explored in SLE. Positive allosteric modulators (PAM) are pharmacological agents that inhibit desensitization of the nicotinic acetylcholine receptor (α7-nAChR), the main anti-inflammatory feature within the cholinergic anti-inflammatory pathway, and may augment α7-dependent cholinergic tone to generate therapeutic benefits in SLE. In the current study, we hypothesized that activating the cholinergic anti-inflammatory pathway at the level of the α7-nAChR with systemic administration of a partial agonist, GTS-21 or a PAM, PNU-120596, would reduce inflammation, eliminating the associated end organ damage in a mouse model of SLE with advanced disease. Further, we hypothesized that these α7 ligands will have central effects and improve behavioral deficits in SLE mice. Female control (NZW) and SLE mice (NZBWF1) were administered GTS-21 (15 mg/kg/day), PNU-120596 (10 mg/kg/day), or vehicle (DMSO) subcutaneously via minipumps for two weeks starting at 33 weeks of age. A subgroup of these mice were subjected to randomized, blinded behavioral tests for sensorimotor and emotional deficits (i.e., open-field, light-dark box and tail suspension tests) pre- and post-drug administration. SLE mice had higher plasma dsDNA autoantibodies, a hallmark of SLE and marker of disease severity, than control mice (9.2e5 ± 1.1e5 vs. 1.6e5 ± 3.9e4 U/mL; p < 0.001), but this increase was not altered by GTS-21 (1.1e6 ± 2.2e5) or PNU-120596 (1.1e6 ± 2.1e5) in SLE mice. The cholinergic anti-inflammatory pathway directly alters splenic inflammation and indirectly alters renal inflammation, so we measured TNF-α in the spleen and renal cortex of control and SLE mice. Splenic and renal TNF-α was 2- and 4-times higher in SLE mice compared to controls (235.0 ± 28.2 and 417.2 ± 122.7; % difference from controls), but neither was altered by GTS-21 (262.5 ± 33.4 and 320.8 ± 91.4) or PNU-120596 (306.1 ± 34.4 and 343.9 ± 97.7) in SLE mice. The anxiety-like behavior (i.e., decrease in locomotion, increase in sleeping, and decrease distance traveled during open-field test in SLE mice compared to controls (all p<0.001)) presented by SLE mice was also not improved by GTS-21 or PNU-120596. Although no significant beneficial effects of α7 ligands were observed in SLE mice at this advanced stage, we predict that potentiating acetylcholine and targeting this receptor earlier in the pathogenesis of SLE may prove to be efficacious and should be addressed in future studies.