Plasma low-density lipoprotein-cholesterol (LDL-C) is mainly taken up and cleared by the hepatocellular LDL receptor (LDL-R). LDL-R gene expression is regulated by the sterol regulatory element binding proteins (SREBPs). Previous studies have shown that curcumin reduces plasma LDL-C and has hypolipidemic and anti-atherosclerotic effects. Herein, we investigated the effect of curcumin on LDL-R expression and its molecular mechanism in HepG2 cells. Curcumin increased LDL-R expression (mRNA and protein) and the resultant uptake of DiI-LDL in a dose- and time-dependent manner. Using a GFP reporter system in a transfected HepG2/SRE-GFP cell line, we found that curcumin activated the sterol regulatory element of the LDL-R promoter. In HepG2/Insig2 cells, curcumin reversed the inhibition of LDL-R expression induced by Insig2 overexpression. These data demonstrate that curcumin increases LDL-R protein expression and uptake activity via the SREBPs pathway. These findings contribute to our further understanding of the cholesterol-lowering and anti-atherosclerotic effects of curcumin.
"Curcumin is the main active polyphenol extracted from the rhizome of Curcuma longa that has been shown to exert multiple effects on inflammation, hyperlipidemia, and atherosclerosis . Particularly, curcumin affects lipid homeostasis/metabolism   , stimulating cholesterol efflux mediated by ABCA1   and reducing cellular cholesterol accumulation  . Furthermore, it has been reported that curcumin, by elevating cytosolic calcium levels, aliviates the NPC phenotype . "
[Show abstract][Hide abstract] ABSTRACT: Exosomes/microvesicles are originated from multivesicular bodies that allow the secretion of endolysosome components out of the cell. In the present work, we investigated the effects of curcumin, a polyphenol, on exosomes/microvesicles secretion in different cells lines, using U18666A as a model of intracellular cholesterol trafficking impairment.
In both HepG2 hepatocarcinoma cells and THP-1 differentiated macrophages, treatment with curcumin affected the size and the localization of endosome/lysosomes accumulated by U18666A, and reduced the cholesterol cell content. To ascertain the mechanism, we analyzed the incubation medium. Curcumin stimulated the release of cholesterol and the lysosomal β-hexosaminidase enzyme, as well as the exosome markers, flotillin-2 and CD63. Electron microscopy studies demonstrated the presence of small vesicles similar to exosomes/microvesicles in the secretion fluid. These vesicles harbored CD63 on their surface, indicative of their endolysosomal origin. These effects of curcumin were particularly intense in cells treated with U18666A.
These findings indicate that curcumin ameliorates the U18666A-induced endolysosomal cholesterol accumulation by shuttling cholesterol and presumably other lipids out of the cell via exosomes/microvesicles secretion. This action may contribute to the potential of curcumin in the treatment of lysosomal storage diseases.
"There may be three possible reasons. Some studies indicated that curcumin up-regulated the expression of low-intensity lipoprotein receptor (LDL-R) protein in human lymphocytes, HEK-293 and mouse macrophages –. Liposoluble sensitizers likely enter cells through LDL-R, while both curcumin and Hydroxyl acetylated curcumin are defined as liposoluble sensitizers. Therefore, Hydroxyl acetylated curcumin maybe enters into macrophages through LDL-R. "
[Show abstract][Hide abstract] ABSTRACT: Curcumin is extracted from the rhizomes of the traditional Chinese herb Curcuma longa. Our previous study indicated curcumin was able to function as a sonosensitizer. Hydroxyl acylated curcumin was synthesized from curcumin to eliminate the unstable hydroxy perssad in our group. The potential use of Hydroxyl acylated curcumin as a sonosensitizer for sonodynamic therapy (SDT) requires further exploration. This study investigated the sonodynamic effect of Hydroxyl acylated curcumin on THP-1 macrophage. THP-1 macrophages were cultured with Hydroxyl acylated curcumin at a concentration of 5.0 μg/mL for 4 hours and then exposed to pulse ultrasound irradiation (0.5 W/cm2 with 1.0 MHz ) for 5 min, 10 min and 15 min. Six hours later, cell viability decreased significantly by CCK-8 assay. After ultrasound irradiation, the ratio of apoptosis and necrosis in SDT group was higher than that in control, Hydroxyl acylated curcumin alone and ultrasound alone. Moreover, the apoptotic rate was higher than necrotic rate with the flow cytometry analysis. Furthermore, Hydroxyl acylated curcumin-SDT induced reactive oxygen species (ROS) generation in THP-1 macrophages immediately after the ultrasound treatment while ROS generation was reduced significantly with the scavenger of singlet oxygen Sodium azide (NaN3). Hydroxyl acylated curcumin-SDT led to a conspicuous loss of mitochondrial membrane potential (MMP) compared with other groups, while MMP was increased significantly with the scavenger of singlet oxygen Sodium azide (NaN3), ROS inhibitor N-acetyl cysteine (NAC) and Mitochondrial Permeability Transition Pore (MPTP) inhibitor Cyclosporin A (CsA). The cytochrome C, cleaved-Caspase-9, cleaved-Caspase-3 and cleaved-PARP upregulated after SDT through Western blotting. These findings suggested that Hydroxyl acylated curcumin under low-intensity ultrasound had sonodynamic effect on THP-1 macrophages via generation of intracellular singlet oxygen and mitochondria-caspase signaling pathway, indicating that Hydroxyl acylated curcumin could be used as a novel sonosensitizer in SDT for atherosclerosis.
PLoS ONE 03/2014; 9(3):e93133. DOI:10.1371/journal.pone.0093133 · 3.23 Impact Factor
"The most consistent finding from the previous studies is a decreased cholesterol level in the blood. The mechanism for such a decrease was suggested to be mediated by an upregulation of LDL receptor [16,17]. The present work demonstrated a novel effect of the component in the gut, i.e. to inhibit the expression of NPC1L1 in the enterocytes. "
[Show abstract][Hide abstract] ABSTRACT: Curcumin is a polyphenol and the one of the principle curcuminoids of the spice turmeric. Its antioxidant, anti-cancer and anti-inflammatory effects have been intensively studied. Previous in vivo studies showed that administration of curcumin also decreased cholesterol levels in the blood, and the effects were considered to be related to upregulation of LDL receptor. However, since plasma cholesterol levels are also influenced by the uptake of cholesterol in the gut, which is mediated by a specific transporter Niemann-Pick Cl-like 1 (NPC1L1) protein, the present study is to investigate whether curcumin affects cholesterol uptake in the intestinal Caco-2 cells.
Caco-2 cells were cultured to confluence. The micelles composed of bile salt, monoolein, and 14C-cholesterol were prepared. We first incubated the cells with the micelles in the presence and absence of ezetimibe, the specific inhibitor of NPC1L1, to see whether the uptake of the cholesterol in the cells was mediated by NPC1L1. We then pretreated the cells with curcumin at different concentrations for 24 h followed by examination of the changes of cholesterol uptake in these curcumin-treated cells. Finally we determined whether curcumin affects the expression of NPC1L1 by both Western blot analysis and qPCR quantification.
We found that the uptake of radioactive cholesterol in Caco-2 cells was inhibited by ezetimibe in a dose-dependent manner. The results indicate that the uptake of cholesterol in this study was mediated by NPC1L1. We then pretreated the cells with 25-100 muM curcumin for 24 h and found that such a treatment dose-dependently inhibited cholesterol uptake with 40% inhibition obtained by 100 muM curcumin. In addition, we found that the curcumin-induced inhibition of cholesterol uptake was associated with significant decrease in the levels of NPC1L1 protein and NPC1L1 mRNA, as analyzed by Western blot and qPCR, respectively.
Curcumin inhibits cholesterol uptake through suppression of NPC1L1 expression in the intestinal cells.
Lipids in Health and Disease 04/2010; 9(1):40. DOI:10.1186/1476-511X-9-40 · 2.22 Impact Factor
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