Background/Purpose: 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, and gastro-intestinal physiology. The splenic nerve (SpN) has been confirmed to be the principal effector nerve for the VN-mediated immune control. Here we tested efficiency of stimulating the nerve plexus around the splenic artery on acute LPS-induced inflammation and collagen-induced arthritis (CIA) in mice and compared it to VN stimulation (VNS) and anti-TNF treatment.

Methods: In an acute LPS mouse model, mice were implanted on the SpN or VN. After recovery from surgery, LPS was injected and splenic nerve stimulation (SNS) or VNS was applied in conscious mice. TNF and norepinephrine (NE) were measured after 90 min. Next, SNS was evaluated in CIA. 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, VNS and 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. Alternatively, mice were treated 3 times/week from day 16 to 45 with 10mg/kg anti-TNF (etanercept) i.p. In curative settings, SNS was applied 6 times a day 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: Stimulating the splenic nerve resulted in an increase of NE (by >100%) in the spleen, as well as a significant reduction in LPS-induced TNF (~50%). This effect was comparable to VNS. In CIA in mice all sham animals developed arthritis, compared to 14% following 6 times per day SNS (p < 0.001).  In contrast, 85% of the animals developed arthritis (p = 0.35) when SNS was applied only once a day. However, 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). Interestingly, SNS treatment inhibited CIA to the same extend as VNS. Moreover, the same electrical parameters dramatically decreased arterial blood pressure during VNS stimulation, which was not the case for SNS. While etanercept treatment reduced clinical scores (p < 0.001) an immediate rebound in clinical score was seen following cessation of treatment, while mice with SNS were still partially protected 35 days after treatment discontinuation (p = 0.013, compared to sham). Finally, when SNS was applied as a therapeutic treatment, clinical scores were significantly reduced (p < 0.001). Analysis of the cells within the spleen after SNS demonstrated a reduction of inflammatory monocytes that correlated with an improvement in clinical scores.

Conclusion: These studies demonstrate that SNS affect the immune cells in the spleen, suppresses pro-inflammatory cytokine production, and reduces clinical symptoms in CIA providing compelling scientific rationale and pre-clinical evidence for the use of splenic neuromodulation in treating RA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/stimulation-of-splenic-neurovascular-bundle-protect-mice-from-developing-collagen-induced-arthritis/