SAT0018 THE THERAPEUTIC EFFECT OF STIMULATION OF THE SPLENIC NEUROVASCULAR BUNDLE IN MICE WITH COLLAGEN-INDUCED ARTHRITIS IS ENHANCED BY CONCOMITANT ANTI-TNF TREATMENT

Abstract

Background:Vagus nerve (VN) stimulation has shown the potential to improve the disease development in animal models of arthritis and in patients with RA. However, the VN can affect respiratory, cardiovascular, endocrine and gastro-intestinal physiology. The splenic nerve (SpN) has been confirmed to be the principal effector nerve for the VN-mediated immune control. Previous studies have shown that stimulating the splenic nerve resulted in an increase of norephiniphrine in the spleen, as well as a significant reduction in LPS-induced TNF (1).Objectives:To test the therapeutic efficiency of splenic nerve stimulation (SNS) in collagen-induced arthritis (CIA) in mice alone or in combination with anti-TNF treatment.Methods:CIA was induced in DBA1/J mice by immunization with bovine type II collagen at days 0 and 21. At day 11, mice were implanted with micro-cuff electrode (CorTec) onto the SpN or VN. From day 16 to day 45, SNS were applied as rectangular charged-balanced biphasic pulses with 650 μA pulse amplitude, 200 µs pulse width at 10 Hz frequency for 2 min 1 or 6 times a day using a Plexon stimulator. In order to investigatedthe mechanism of action in more detail, propranolol, a beta-adrenergic receptor (β-AR) antagonist, was added to the drinking water of mice receiving SNS. In addition, a control group was treated with anti-TNF (etanercept, 3 times/week; 10mg/kg i.p.). In curative settings, SNS and/or anti-TNF treatment was applied starting when mice scored positive for 3 consecutive days. Clinical arthritis was determined by visual examination of swelling and redness of the paws and measurement of paw thickness. Sham mice were undergoing the same procedure but did not receive stimulation.Results:In CIA in mice all sham animals developed arthritis, compared to only 14% following six times per day SNS (p <0.001) in a prophylactic setting. In contrast, 85% of the animals developed arthritis (p = 0.35) when SNS was applied only once a day. In both stimulated groups a significant decrease in clinical scores and paw thickness was observed compared to unstimulated group (p < 0.01 and p < 0.05, respectively). While etanercept treatment reduced clinical scores (p <0.001) an immediate rebound in clinical score was seen following treatment arrest, while mice with SNS were still partially protected 35 days after treatment discontinuation (p = 0.013, compared to sham). Propranolol inverted the effect of SNS in CIA mice. Finally, when SNS was applied as a curative treatment, clinical scores were significantly reduced (p < 0.001). Importantly, these clinical scores even further decreased when anti-TNF treatment was given to mice receiving SNS.Conclusion:These studies demonstrate that SNS suppresses pro-inflammatory cytokine production, and reduces clinical symptoms in mice with CIA which is at least partially mediated by the β-AR. The additive effect of anti-TNF in reducing the clinical scores demonstrates that that mechanism of action of SNS is not primarilys mediated by reducing TNF levels. Moreover, anti-TNF potentiating the inhibitory effect of SNS is supporting a combined use of these treatments, or even a combination of SNS with other biologicals, to treat RA, potentially getting more patients closer to remission. In conclusion, the data is providing compelling scientific rationale and pre-clinical evidence that splenic neuromodulation might be a new treatment modality for RA.