Cholesterol Crystals as the Main Trigger of Interleukin-6 Production through Innate Inflammatory Response in Human Spontaneously Ruptured Aortic Plaques

This study aimed to clarify whether cholesterol crystals (CCs) are the main trigger of innate inflammation in human spontaneously ruptured aortic plaques (SRAPs).This study included 260 SRAPs collected during nonobstructive general angioscopy (NOGA) from 126 patients with confirmed or suspected coronary artery disease. Interleukin (IL)-6 levels in SRAPs were measured. IL-6 levels in the Valsalva sinus and femoral or brachial arteries were measured. IL-6 ratios (the IL-6 level in SRAPs and arteries divided by the IL-6 level at the Valsalva sinus at the beginning of the aorta) were calculated. Quantitative analysis of CCs was performed from SRAPs. The correlation between the count of CCs and IL-6 levels in SRAPs and that between the counts of CCs and IL-6 ratios in SRAPs were analyzed.The IL-6 levels in SRAPs were 3.4 [2.1, 7.2] pg/mL, and the IL-6 ratio (median [interquartile range]) in SRAPs was 1.10 [1.00, 1.26]. CCs were detected in 94 of 260 SRAPs (36%). The count of CCs was 11,590 (95% confidence interval, 2,386-30,113) per 10 mL in CC-positive samples. There was a moderate correlation between the counts of CCs and IL-6 ratios in SRAPs (r=0.49, r＜0.0001), whereas there was no correlation between the count of CCs and IL-6 levels in SRAPs. The IL-6 ratios of the brachial and femoral arteries were 1.06 (95% CI, 0.99-1.20) and 1.11 (95% CI, 1.04-1.20), respectively.CC is the main trigger of IL-6 production through innate inflammatory response in human SRAPs in situ.