Vagus nerve stimulation inhibits cytokine production and attenuates disease severity in rheumatoid arthritis

Abstract

Rheumatoid arthritis (RA) is a heterogeneous, prevalent, chronic autoimmune disease characterized by painful swollen joints and significant disabilities. Symptomatic relief can be achieved in up to 50% of patients using biological agents that inhibit tumor necrosis factor (TNF) or other mechanisms of action, but there are no universally effective therapies. Recent advances in basic and preclinical science reveal that reflex neural circuits inhibit the production of cytokines and inflammation in animal models. One well-characterized cytokine-inhibiting mechanism, termed the "inflammatory reflex," is dependent upon vagus nerve signals that inhibit cytokine production and attenuate experimental arthritis severity in mice and rats. It previously was unknown whether directly stimulating the inflammatory reflex in humans inhibits TNF production. Here we show that an implantable vagus nerve-stimulating device in epilepsy patients inhibits peripheral blood production of TNF, IL-1β, and IL-6. Vagus nerve stimulation (up to four times daily) in RA patients significantly inhibited TNF production for up to 84 d. Moreover, RA disease severity, as measured by standardized clinical composite scores, improved significantly. Together, these results establish that vagus nerve stimulation targeting the inflammatory reflex modulates TNF production and reduces inflammation in humans. These findings suggest that it is possible to use mechanism-based neuromodulating devices in the experimental therapy of RA and possibly other autoimmune and autoinflammatory diseases.

Keywords: cytokines; inflammatory reflex; rheumatoid arthritis; tumor necrosis factor; vagus nerve.

Fig. 1.

Inflammatory reflex activation reduces whole-blood LPS-induced TNF production in epilepsy patients. Electrical stimulation of the vagus nerve in humans inhibits whole-blood LPS-induced TNF release. Blood was obtained from epilepsy patients (n = 7) undergoing implantation of a vagus nerve-stimulation device at different time points: before anesthesia induction and before vagus nerve stimulation; after anesthesia induction and before vagus nerve stimulation (pre-VNS); and 4 h after vagus nerve stimulation (post-VNS). Whole blood was incubated with LPS and TNF (A), IL-6 (B), and IL-1β (C) levels in plasma were determined after 4 h in culture. The significance of the differences between mean values at each time point was tested by unpaired ANOVA (*P < 0.05, **P < 0.01). Data are shown as mean ± SEM.

Fig. 2.

The effects of inflammatory reflex activation on whole-blood LPS-induced TNF production and disease activity in RA patients. (A) Schematic of the RA study design. D −21 to D84 indicate study visit days. The stimulation schedule and timing of assessments are shown. (B) Mean LPS-induced TNF production in the combined RA cohort (n = 17) at study days −21, 0, 42, 56, and 84; visit means are designated by bars, and error bars indicate SEM. Differences in means were tested for significance by paired t test: *P < 0.05 vs. d −21; ⁺P < 0.01 vs. d 0; ^{^}P < 0.01 vs. d 42; ^#P < 0.01 vs. d 56. (C) The mean change in DAS2 8-CRP from baseline by study visit day for cohort I (patients failing methotrexate treatment), cohort II (patients failing treatment by multiple biologic agents), and combined cohorts. The significance of the mean change by paired t test between visits is shown: *P < 0.05 vs. d −21; ^//P < 0.01 vs. d −21; ⁺P < 0.001 vs. d −21; ^#P < 0.001 vs. d 42; ^P < 0.05 vs. d 42). (D) Linear regression analysis comparing the changes in the DAS28-CRP and the percent change in TNF release from study day −21 measured at each individual visit for each patient in the combined cohort. Changes in the DAS28-CRP and TNF release are significantly correlated by Pearson’s test (r = 0.384, P < 0.0001). (E) Mean change in the DAS28-CRP and mean LPS-induced TNF release over time by study visit day. Changes in the DAS28-CRP and TNF release follow a similar temporal pattern in response to initial simulation, stimulation withdrawal, and stimulation reinitiation.

Fig. S1.

Individual RA patient DAS28-CRP. Individual patient DAS28-CRP over time are shown for cohorts I (7 patients) (A) and II (10 patients) (B).

Fig. S2.

Clinical response and remission rates of RA patients with respect to screening day −21. (A and B) The ACR20, ACR50, and ACR70 response rates in cohort I, cohort II, and the combined cohorts are shown at study day 42 (A), and study day 84 (B). (C and D) The rates of EULAR moderate and good response and remission in cohorts I and II and the combined cohorts are shown at study day 42 (C) and study day 84 (D). The patient with Whipple disease excluded from efficacy analysis had an ACR20 response and a good EULAR response on day 42 and no ACR response and a moderate EULAR response on day 84.

Fig. 3.

Modulation of serum cytokines. Serum from each patient in the combined cohort was analyzed for multiple analytes at day 42. (A, C, and E) Individual patient values for EULAR nonresponders and responders are shown for IL-6 (A), IL-8 (C), and IL-17 (E) levels. The significance of differences between mean values at each time point was tested by unpaired t test (**P < 0.01). Horizontal bars indicate mean ± SEM. (B, D, and F) Linear regression analysis comparing analyte level at day 42 to the change in the DAS28-CRP from study day −21 to day 42. The change in the DAS28-CRP is significantly correlated to IL-6 release (r = 0.707, P = 0.002) (B) but not to IL-8 release (r = 0.261, P = 0.31) (D) or IL-17 release (r = 0.384, P = 0.07) (F).

Fig. S3.

The Cyberonics vagus nerve-stimulation system. The implanted system has two components: a bipolar lead containing two helical coil electrodes and a helical anchor tether that were wrapped around the cervical vagus nerve, and the pulse generator that is placed within a subcutaneous pocket in the chest wall. (A) Schematic diagram of the system. The lead was tunneled subcutaneously from the neck to the pulse generator and inserted into the lead attachment port on the generator. (B) Images of the helical electrode and pulse generator.