Near-Infrared Autofluorescence in Atherosclerosis Associates With Ceroid and Is Generated by Oxidized Lipid-Induced Oxidative Stress

Abstract

Objective: Near-infrared autofluorescence (NIRAF) of atherosclerosis associates with intraplaque hemorrhage and is detectable in living patients with coronary artery disease. However, further mechanisms underlying NIRAF generation have not been fully characterized. Here, we investigated the role of lipids and oxidative stress in NIRAF generation in atherosclerosis and in vitro in human macrophages. Approach and Results: In N=15 human carotid endarterectomy specimens, we investigated the spatial distribution of lipid, intraplaque hemorrhage, and NIRAF (ex/em 630/650 nm). Plaque NIRAF associated with both Sudan black (SB)-positive lipids ( r =0.53, P =0.023) and GPA (glycophorin A)-positive intraplaque hemorrhage ( r =0.48, P =0.043). Plaque NIRAF also localized with lipid and specifically insoluble lipid (ceroid) and iron. Intriguingly, some NIRAF-positive areas were Sudan black-positive but GPA-negative. Studies on human macrophages investigated further the role of lipids in NIRAF generation. OxLDL (Oxidized low-density lipoprotein) and hemoglobin, but not LDL, generated NIRAF in both THP-1 cells and monocyte-derived macrophages. In oxLDL-treated THP-1 cells, higher NIRAF, lipid peroxidation products, and intracellular oxidative stress markers evolved ( P <0.001 versus LDL). The antioxidants α-tocopherol and N-acetylcysteine suppressed NIRAF generation and oxidative stress. Conclusions: In human atherosclerosis and human macrophages in vitro, NIRAF colocalizes with lipid and specifically insoluble lipid or ceroid. In vitro studies further show that oxidized LDL generates NIRAF, oxidative stress, and lipid peroxidation products. These results demonstrate a new pathway for NIRAF generation through oxidized lipid-driven oxidative stress and support ceroid as a source of NIRAF in human atherosclerosis. These findings may inform future clinical intracoronary NIRAF imaging studies of patients with coronary artery disease.

Protective Effect of Isoorientin on Oleic Acid-Induced Oxidative Damage and Steatosis in Rat Liver Cells

“…Lipid metabolic disorders often produce ROS, which leads to oxidative damage. Studies have also shown that ROS can regulate lipid metabolism (Albaghdadi et al, 2021;Chen et al, 2021;Li et al, 2021). Aberrant metabolism of TG is the main cause of fatty liver, and the most intuitive manifestation in steatosis is the accumulation of TG (Yu et al, 2021;Zhang Z. et al, 2021).…”

Combined near infrared photoacoustic imaging and ultrasound detects vulnerable atherosclerotic plaque

“…Near-infrared autofluorescence (NIRAF) has been associated with lipids and intraplaque hemorrhage. Macrophages, which are a marker of a vulnerable plaque, phagocytose extravasated red blood cells, degrade heme to bilirubin, and are involved in the formation of insoluble lipids or ceroids 29,31 . Here we show that the aforementioned endogenous near-infrared biomarkers, especially in colocalization with macrophages, can be detected by PAI.…”

“…Recently, bilirubin and other heme degradation products and insoluble lipid in atherosclerotic plaques have been evaluated as to their autofluorescence properties in the near-infrared (680 nm) range 29 . The hemoglobin degradation products represent a pathological process indicative of intraplaque hemorrhage and therefore serve as an important biomarker for vulnerable plaque [29][30][31] . However, near-infrared autofluorescence (NIRAF) in the 650-700 nm range suffers from limited penetration depth and spatial resolution; and therefore, photoacoustic techniques are attractive 22,32 .…”

Near-Infrared Autofluorescence (NIRAF) in Atherosclerotic Plaque Dissociates from Intraplaque Hemorrhage and Bilirubin

“…Htun et al reported bilirubin (formed from biliverdin by biliverdin reductase) to be the likely source of NIRAF, based on the co-localization of bilirubin with IPH in plaque, and the positive association between plaque bilirubin concentrations and NIRAF in the TS mouse model of plaque instability [ 2 ]. In apparent contrast, Albaghdadi et al observed elevated NIRAF in the absence of co-localized IPH and bilirubin in human carotid endarterectomy specimens, and instead suggested an insoluble oxidized lipid or ceroid as a source of NIRAF [ 5 ]. Thus, the roles of IPH and bilirubin in the NIRAF of atherosclerotic plaque remain unclear; however, knowledge of the underlying molecular mechanism(s) is important to better understand the biological relevance and clinical significance of NIRAF-based imaging strategies.…”