Focused ultrasound stimulation of the inflammatory reflex at the spleen ameliorates pulmonary arterial hypertension in rodents

Abstract Background Inflammation is a major contributor in pulmonary arterial hypertension (PAH) pathogenesis. Non-invasive, focused ultrasound stimulation (FUS) of the spleen activates the neuroimmune inflammatory reflex (IR) and suppresses systemic inflammation [1]. Purpose We aimed to explore whether daily FUS of the spleen improves haemodynamics and biomarkers by modulating the IR, in a rat model of PAH. Methods Sprague-Dawley rats (n=12) were injected s.c. with Sugen5416 (VEGF receptor inhibitor) and then, were placed in a hypoxic chamber (FiO2=10%) for 21 days, followed by 14 days of re-exposure to normoxia (FiO2=10%). At day 21, rats were randomized to either FUS (n=6) or sham-stimulation of the spleen (n=6). Each FUS- or sham-stimulation session consisted of 12 minutes. After 14 days of treatment, in a terminal experiment, right ventricular systolic pressure (RVSP) and arterial pressure were measured invasively, as well as biomarkers, in each animal (Figure 1A). Results FUS significantly reduced RVSP compared with the sham-stimulation (Mean±SEM, 50.83±3.57 mmHg vs 72.50±5.81; p=0.009), resulting in a 30% relative reduction (Figure 1B). Mean systemic arterial pressure was similar in the 2 groups (Mean±SEM, 79.83±3.73 mmHg vs. 87.00±2.95; p=0.137) (Figure 1C), as was the change in heart rate between day 1 and day 14 of treatment period (−19.53±5.36% vs. −16.79±3.1, p=0.61) (Figure 1D). Consistently, plasma brain natriuretic peptide (BNP) levels are reduced in the FUS group (119.45±19.93 ng/μl vs. 319.39±91.85; p=0.019), indicative of reduced myocardial wall stress in the FUS group (Figure 1E). Conclusion Non-invasive FUS of the spleen reduced RVSP by ∼30% and BNP without significantly affecting systemic pressure or heart rate, in rats with severe PAH. Non-invasive FUS, by modulating the IR, may exert an anti-inflammatory effect in PAH. FUS of the spleen is noninvasive, safe, widely available and easy to perform, and should be further explored as a possible therapeutic option in PAH. Funding Acknowledgement Type of funding sources: Private hospital(s). Main funding source(s): Northwell Health