Targeted stimulation of the vagus nerve reduces renal injury in female mice with systemic lupus erythematosus

Abstract

Pharmacological stimulation of the vagus nerve has been shown to suppress inflammation and reduce blood pressure in a murine model of systemic lupus erythematosus (SLE) that is characterized by hypertension, inflammation, renal injury and dysautonomia. The present study aims to directly stimulate vagal nerves at the level of the dorsal motor nucleus of the vagus (DMV) using designer receptors exclusively activated by designer drugs (DREADDs) to determine if there is similar protection and confirm mechanism. Female NZBWF1/J (SLE) mice and NZW/LacJ mice (controls, labeled as NZW throughout) received bilateral microinjections of pAAV-hSyn-hM3D(Gq)-mCherry or control virus into the DMV at 31 weeks of age. After two weeks of recovery and viral transfection, the DREADD agonist clozapine-N-oxide (CNO; 3 mg/kg) was injected subcutaneously for an additional 14 days. At 35 weeks, mean arterial pressure (MAP; mmHg) was increased in SLE mice compared to NZW mice, but selective activation of DMV neurons did not significantly alter MAP in either group. SLE mice had higher indices of renal injury including albumin excretion rate (μg/day), glomerulosclerosis index, interstitial fibrosis, neutrophil gelatinase-associated lipocalin (NGAL), and kidney injury molecule-1 (KIM-1) compared to NZW mice. Selective DMV neuronal activation reduced albumin excretion rate, glomerulosclerosis, interstitial fibrosis, and NGAL in SLE mice but not NZW mice. Together, these data indicate that selective activation of neurons within the DMV by DREADD protects the kidney suggesting an important role of vagus-mediated pathways in the progression of renal injury in SLE.

Keywords: Cholinergic anti-inflammatory pathway; DREADD; Glomerulosclerosis; Inflammation; Kidney injury; SLE; Vagal nerves.

Fig. 1.

A. Representative figure of the site of virus microinjection within the DMV. B. Representative figure of acute activation of DMV neurons with DREADD and clozapine N-oxide (CNO) in an anesthetized NZW mice. Targeted acute vagus nerve activation reduced heart rate and increased vagus nerve activity. Arrow indicates the time of subcutaneous CNO injection (3 mg/kg).

Fig. 2.

Activation of DMV neurons did not significantly alter blood pressure and disease severity. A. SLE mice had increased mean arterial pressure compared to NZW mice and DMV neurons activation with DREADD did not change this outcome. n = 4–5/group, *p < 0.05 vs. NZW/Control. B. Disease severity evaluated by anti-dsDNA autoantibodies did not change after DMV activation in SLE and NZW mice. n = 3–5/group. Data were analyzed using two-way ANOVA followed by Holm-Sidak post-hoc. Results of the ANOVA are shown on the graph.

Fig. 3.

DMV neuron activation did not have significant impact on spleen and kidney inflammation in SLE mice. SLE mice had increased spleen (A) tumor necrosis factor alpha (TNFα) protein expression compared to NZW mice. Data were analyzed using two-way ANOVA followed by Holm-Sidak post-hoc.

Fig. 4.

Central activation of the cholinergic anti-inflammatory pathway decreases renal injury in SLE female mice. A. Albumin excretion rate was increased in SLE compared to NZW mice and DMV activation decreased albumin excretion in SLE although not statistically different. n = 4–5/group. B. SLE mice had significantly higher glomerulosclerosis score compared to NZW mice and DMV neuronal activation decreased glomerular injury in SLE mice. Representative figures shown. C. SLE mice had increased fibrosis compared to NZW mice and DMV neuronal activation decreased fibrosis in SLE mice. D. Urinary Kim1 (pg/mL) and E. NGAL (pg/mL) were increased in SLE mice compared to NZW mice and DVMV neuron activation decreased both markers in female mice with SLE. Data are also presented normalized to urinary creatinine.