O47 THE ROLE OF IL-33 AND ST2 IN THE MODULATION OF TARGET ORGAN DAMAGE IN ANGIOTENSIN II-DEPENDENT HYPERTENSION

Introduction: Hypertension is associated with a chronic inflammatory state and aberrant immune system activity. Interleukin-33/suppression of tumorigenicity 2 (IL-33/ST2) signalling axis is important in the modulation of atherosclerosis and cardiovascular fibrosis. We aimed to evaluate the modulation of IL-33 and ST2 in hypertensive mouse models and patients. Methods and Results: Hypertension was induced by a 14-day infusion of Ang-II (490ng/min/kg) in 12-week-old WT C57BL/6, ST2KO, IL33KO mice. IL-33 and ST2 mRNA and protein were evaluated using qPCR and Western blot in WT mice. Ang II-infusion significantly increased IL-33 and ST2 protein expression in target organs related to hypertension, particularly the aorta (1.0±0.1 vs 2.8±0.2, p<0.0001, and 0.963±0.068 vs 2.094±0.231, p=0.002, respectively). Further, mRNA expression of IL-33 and ST2 was elevated in hypertensive aortas when compared with control (1.0±0.053 vs 1.76±0.271, p=0.0185 and 1.0±0.039 vs 1.978±0.221, p=0.0039, respectively). IHC from WT mice illustrated the localisation of IL-33 and ST2 in Ang-II aortas in ECs and SMCs. Further in human hypertensive mammary arteries, the localisation was. In-vivo, IL33KO and ST2KO mice showed no altered BP at baseline or after 14 days of Ang-II compared to WT littermates. ST2KO Ang-II mice showed protection against endothelial dysfunction compared to WT Ang-II mice through isometric tension studies (p=0.0317). Additionally, Ang-II-induced IL33KO and ST2KO mice worsen cardiac fibrosis compared to WT littermates (p=0.0005,p<0.0001, respectively). Conclusion: Both IL-33 and its receptor, ST2 are increased in the vascular and perivascular tissues in hypertension. Additionally, the IL-33/ST2 axis has a role in regulating cardiac fibrosis.