Natural Biflavonoids Modulate Macrophage–Oxidized LDL Interaction In Vitro and Promote Atheroprotection In Vivo

Abstract

The accumulation of oxidized ApoB-100-containing lipoproteins in the vascular intima and its subsequent recognition by macrophages results in foam cell formation and inflammation, key events during atherosclerosis development. Agents targeting this process are considered potentially atheroprotective. Since natural biflavonoids exert antioxidant and anti-inflammatory effects, we evaluated the atheroprotective effect of biflavonoids obtained from the tropical fruit tree Garcinia madruno. To this end, the pure biflavonoid aglycones morelloflavone (Mo) and volkensiflavone (Vo), as well as the morelloflavone’s glycoside fukugiside (Fu) were tested in vitro in primary macrophages, whereas a biflavonoid fraction with defined composition (85% Mo, 10% Vo, and 5% Amentoflavone) was tested in vitro and in vivo. All biflavonoid preparations were potent reactive oxygen species (ROS) scavengers in the oxygen radical absorbance capacity assay, and most importantly, protected low-density lipoprotein particle from both lipid and protein oxidation. In biflavonoid-treated macrophages, the surface expression of the oxidized LDL (oxLDL) receptor CD36 was significantly lower than in vehicle-treated macrophages. Uptake of fluorescently labeled oxLDL and cholesterol accumulation were also attenuated in biflavonoid-treated macrophages and followed a pattern that paralleled that of CD36 surface expression. Fu and Vo inhibited oxLDL-induced ROS production and interleukin (IL)-6 secretion, respectively, whereas all aglycones, but not the glucoside Fu, inhibited the secretion of one or more of the cytokines IL-1β, IL-12p70, and monocyte chemotactic protein-1 (MCP-1) in lipopolysaccharide (LPS)-stimulated macrophages. Interestingly, in macrophages primed with low-dose LPS and stimulated with cholesterol crystals, IL-1β secretion was significantly and comparably inhibited by all biflavonoid preparations. Intraperitoneal administration of the defined biflavonoid fraction into ApoE−/− mice was atheroprotective, as evidenced by the reduction of the atheromatous lesion size and the density of T cells and macrophages infiltrating the aortic root; moreover, this treatment also lowered the circulating levels of cholesterol and the lipid peroxidation product malondialdehyde. These results reveal the potent atheroprotective effects exerted by biflavonoids on key events of the oxLDL–macrophage interphase: (i) atheroligand formation, (ii) atheroreceptor expression, (iii) foam cell transformation, and (iv) prooxidant/proinflammatory macrophage response. Furthermore, our results also evidence the antioxidant, anti-inflammatory, hypolipemiant, and atheroprotective effects of Garcinia madruno’s biflavonoids in vivo.

Oxidized LDL triggers changes in oxidative stress and inflammatory biomarkers in human macrophages

“…3 B ). Previous studies have confirmed this behavior in murine macrophages [32] , [56] , [57] , showing that ROS production increased over a period of 1–4 h, reaching a plateau at 8 h of oxLDL exposure [56] .

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Biflavonoid as potential 3-chymotrypsin-like protease (3CLpro) inhibitor of SARS-Coronavirus

“…From the zingiberaceae family, new biflavonoids with flavanone-chalcone type can be found in fingerroot ( Boesenbergia rotunda ) [41] . The pure biflavonoid with aglycones morelloflavone (Mo) type, volkensiflavone (Vo) type, as well as the morelloflavone’s glycoside fukugiside (Fu) type was characterized in Garcinia madruno [42] . The genus of garcinia again shows its resource of biflavonoid by the discovery of seven compounds including volkensiflavone, fukugetin, fukugeside, GB 1a, GB 1a glucoside, GB 2a, and GB 2a glucoside from Garcinia xanthochymus fruits [43] .…”

Novel Phytoconstituents of an Aqueous Pod Extract of Prosopis Cineraria (L.) Druce Attenuate Atherosclerotic Plaque and Hypercholesterolemia in Rabbits

“…An FTIR Spectrophotometer (Bruker Co., Germany) equipped with a standard detector and a germanium beam splitter, interfaced with a computer and analytical software, was utilized for the analysis. The KBr pellet technique was used to obtain a spectrum in the mid IR region of 400-4000 cm 1 . The spectrum was characterized using the attenuated Total Re ectance (ATR) technique [22].…”

“…The enzyme, 3-hydroxy-3-methylglutary-coenzyme A (HMG-CoA) reductase plays a key role in regulating the cholesterol biosynthetic pathway. Inhibition of HMG-CoA reductase activity will reduce cholesterol synthesis and thus increase hepatic uptake of low density lipids (LDL) by modulation of LDL receptors [1].…”