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Otis JP, Shen MC, Caldwell BA, Reyes Gaido OE, Farber SA. Dietary cholesterol and apolipoprotein A-I are trafficked in endosomes and lysosomes in the live zebrafish intestine. Am J Physiol Gastrointest Liver Physiol 2019; 316:G350-G365. [PMID: 30629468 PMCID: PMC6415739 DOI: 10.1152/ajpgi.00080.2018] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Difficulty in imaging the vertebrate intestine in vivo has hindered our ability to model nutrient and protein trafficking from both the lumenal and basolateral aspects of enterocytes. Our goal was to use live confocal imaging to increase understanding of intestinal trafficking of dietary cholesterol and apolipoprotein A-I (APOA-I), the main structural component of high-density lipoproteins. We developed a novel assay to visualize live dietary cholesterol trafficking in the zebrafish intestine by feeding TopFluor-cholesterol (TF-cholesterol), a fluorescent cholesterol analog, in a lipid-rich, chicken egg yolk feed. Quantitative microscopy of transgenic zebrafish expressing fluorescently tagged protein markers of early, recycling, and late endosomes/lysosomes provided the first evidence, to our knowledge, of cholesterol transport in the intestinal endosomal-lysosomal trafficking system. To study APOA-I dynamics, transgenic zebrafish expressing an APOA-I fluorescent fusion protein (APOA-I-mCherry) from tissue-specific promoters were created. These zebrafish demonstrated that APOA-I-mCherry derived from the intestine accumulated in the liver and vice versa. Additionally, intracellular APOA-I-mCherry localized to endosomes and lysosomes in the intestine and liver. Moreover, live imaging demonstrated that APOA-I-mCherry colocalized with dietary TF-cholesterol in enterocytes, and this colocalization increased with feeding time. This study provides a new set of tools for the study of cellular lipid biology and elucidates a key role for endosomal-lysosomal trafficking of intestinal cholesterol and APOA-I. NEW & NOTEWORTHY A fluorescent cholesterol analog was fed to live, translucent larval zebrafish to visualize intracellular cholesterol and apolipoprotein A-I (APOA-I) trafficking. With this model intestinal endosomal-lysosomal cholesterol trafficking was observed for the first time. A new APOA-I fusion protein (APOA-I-mCherry) expressed from tissue-specific promoters was secreted into the circulation and revealed that liver-derived APOA-I-mCherry accumulates in the intestine and vice versa. Intestinal, intracellular APOA-I-mCherry was observed in endosomes and lysosomes and colocalized with dietary cholesterol.
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Affiliation(s)
- Jessica P. Otis
- 1Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland
| | - Meng-Chieh Shen
- 1Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland
| | - Blake A. Caldwell
- 1Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland
| | - Oscar E. Reyes Gaido
- 1Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland,2Department of Biology, Johns Hopkins University, Baltimore, Maryland
| | - Steven A. Farber
- 1Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland,2Department of Biology, Johns Hopkins University, Baltimore, Maryland
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Anami Y, Kobori S, Sakai M, Kasho M, Nishikawa T, Yano T, Matsuda H, Matsumura T, Takemura T, Shichiri M. Human beta-migrating very low density lipoprotein induces foam cell formation in human mesangial cells. Atherosclerosis 1997; 135:225-34. [PMID: 9430372 DOI: 10.1016/s0021-9150(97)00166-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
To elucidate the mechanism of foam cell formation in the mesangial region of a kidney observed in a familial type III hyperlipoproteinemic patient presenting with diabetes mellitus and nephrotic syndrome, we have examined, in the present study, the effect of human beta-VLDL (apo E2/E2) on foam cell formation in human mesangial cells, since an increase in beta-VLDL is a characteristic feature of this patient. Human beta-VLDL (apo E2/E2) induced foam cell formation in human mesangial cells. The binding of [125I]LDL to human mesangial cells was inhibited completely by both LDL and beta-VLDL. On the other hand, the binding of [125I]beta-VLDL was completely inhibited by beta-VLDL, but partially by LDL. The LDL receptor, but not the VLDL receptor was down-regulated by accumulation of cholesteryl esters. These results suggest that human beta-VLDL (apo E2/E2)-induced foam cell formation in mesangial cells is mediated through both the LDL receptor pathway and the beta-VLDL specific pathway, in which the VLDL receptor is one of the candidates.
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Affiliation(s)
- Y Anami
- Department of Metabolic Medicine, Kumamoto University School of Medicine, Japan
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Yano T, Kobori S, Sakai M, Anami Y, Matsumura T, Matsuda H, Kasho M, Shichiri M. Beta-very low density lipoprotein induces triglyceride accumulation through receptor mediated endocytotic pathway in 3T3-L1 adipocytes. Atherosclerosis 1997; 135:57-64. [PMID: 9395273 DOI: 10.1016/s0021-9150(97)00146-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
To elucidate the mechanism of triglyceride (TG) accumulation in adipocytes induced by TG-rich lipoproteins, we examined the effect of beta-very low density lipoprotein (beta-VLDL) on TG accumulation in 3T3-L1 adipocytes. Beta-VLDL did not induce TG accumulation in 3T3-L1 preadipocytes but in 3T3-L1 adipocytes. TG accumulation was significantly inhibited by cytochalasin B, an inhibitor of receptor mediated endocytosis. In contrast, cytochalasin B did not inhibit free fatty acid induced TG accumulation in adipocytes. The binding of [125I]beta-VLDL to preadipocytes was inhibited completely by both beta-VLDL and LDL. In sharp contrast, the binding of [125I]beta-VLDL to adipocytes was inhibited completely by beta-VLDL, but partially by LDL. The VLDL receptor mRNA was only expressed in adipocytes. These results suggest that beta-VLDL induced TG accumulation in adipocytes may be mediated through the VLDL receptor pathway.
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Affiliation(s)
- T Yano
- Department of Metabolic Medicine, Kumamoto University School of Medicine, Honjo, Japan
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Sviridov D, Sasahara T, Pyle LE, Nestel PJ, Fidge NH. Antibodies against high-density lipoprotein binding proteins enhance high-density lipoprotein uptake but do not affect cholesterol efflux from rat hepatoma cells. Int J Biochem Cell Biol 1997; 29:583-8. [PMID: 9363635 DOI: 10.1016/s1357-2725(96)00174-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
High-density lipoprotein plays a key role in the reverse cholesterol transport pathway as well as in the delivery of cholesterol to the liver and steroidogenic tissues. Metabolism of high-density lipoprotein is determined by one of its apolipoproteins, apolipoprotein A-I; however, the identity and function of cellular protein which binds high-density lipoprotein remains unclear. The effect of antibodies against rat high-density lipoprotein binding proteins, HB1 and HB2, on high-density lipoprotein metabolism in a rat hepatoma cell line were studied. Cells were preincubated with the antibodies and 125I-labeled high-density lipoprotein binding and uptake as well as cholesterol biosynthesis and cholesterol efflux to human plasma or isolated high-density lipoprotein were studied. Both antibodies reacted specifically with HB1 and HB2 on the ligand and Western blots, but their binding was not blocked by high-density lipoprotein. Both antibodies inhibited 125I-labeled high-density lipoprotein binding to cells by 20-40%, but stimulated 125I-labeled high-density lipoprotein uptake by up to 2.5-fold. The antibodies had no effect on cholesterol efflux or on cholesterol synthesis. It is concluded that high-density lipoprotein binding proteins, HB1 and HB2, may be involved in high-density lipoprotein uptake in the liver rather than in mediating cholesterol efflux.
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Affiliation(s)
- D Sviridov
- Baker Medical Research Institute, Prahran, Australia
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Sato Y, Kobori S, Sakai M, Yano T, Higashi T, Matsumura T, Morikawa W, Terano T, Miyazaki A, Horiuchi S, Shichiri M. Lipoprotein(a) induces cell growth in rat peritoneal macrophages through inhibition of transforming growth factor-beta activation. Atherosclerosis 1996; 125:15-26. [PMID: 8831923 DOI: 10.1016/0021-9150(96)05829-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
To elucidate the atherogenicity of lipoprotein(a) (Lp(a)), we examined its growth-stimulating activity in rat resident peritoneal macrophages. When macrophages were incubated with Lp(a), cell numbers were increased 1.5-fold as compared with control macrophages. Furthermore, apolipoprotein(a) (apo(a)), a plasminogen-like glycoprotein which is covalently attached to a low density lipoprotein-like particle (Lp(a)), also induced macrophage growth, while the growth-stimulating effect of Lp(a-) was negligible. These results suggest that apo(a) plays an active role in the mitogenic activity of Lp(a). Lp(a)-induced macrophage growth was inhibited by exogenously added active transforming growth factor-beta (TGF-beta) dose-dependently, and also by the addition of plasmin, which converts latent TGF-beta to an active form. Moreover, the amounts of endogenous active TGF-beta in the medium were significantly reduced by the incubation with Lp(a). It is evident from these results that Lp(a) induces macrophage growth by inhibiting TGF-beta activation. The capacity of Lp(a) to stimulate macrophage growth shown here could be novel atherogenic function of Lp(a).
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Affiliation(s)
- Y Sato
- Department of Metabolic Medicine, Kumamoto University School of Medicine, Japan
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Bocharov AV, Huang W, Vishniakova TG, Zaitseva EV, Frolova EG, Rampal P, Bertolotti R. Glucocorticoids upregulate high-affinity, high-density lipoprotein binding sites in rat hepatocytes. Metabolism 1995; 44:730-8. [PMID: 7783657 DOI: 10.1016/0026-0495(95)90185-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Glucocorticoid hormones (GL) regulate high-density lipoprotein (HDL) plasma concentrations by increasing synthesis and secretion of HDL by the liver. However, little is known about the effect of GL on the uptake and processing of HDL by hepatocytes (HEP). To investigate this question, we studied the effects of dexamethasone (DEX) on the expression of high-affinity HDL-binding sites via the specific binding and internalization of iodine-labeled apolipoprotein E (apo E)-free HDL3 in a culture of rat HEP. Specific binding and internalization of HDL3 decreased by 60% in cells cultured in the absence of DEX for 48 hours. At concentrations of 10(-7) and 10(-5) mol/L, DEX prevented the decrease, maintaining specific binding and internalization versus the control level (at 24 hours). HDL-binding sites with a Kd of 20 micrograms/mL were revealed on the surface of cultured HEP. HEP demonstrated a greater binding capacity in the presence of DEX at concentrations of 10(-7) and 10(-5) mol/L (125 v 45 ng/mg cell protein). The effect of the hormone has demonstrated to be dose-dependent at concentrations between 10(-9) and 10(-7) mol/L, leveling off at 10(-7). Higher concentrations did not induce a further increase in specific binding and internalization. Withdrawal of the hormone from culture medium was associated with a decrease in specific binding of the ligand by 60% in the following 24 hours. To investigate the effect of glucocorticoid deficiency on liver uptake of HDL in vivo, specific binding and internalization were studied in a culture of HEP isolated from adrenalectomized rats (AER) at 2 hours after seeding.(ABSTRACT TRUNCATED AT 250 WORDS)
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Nishikawa T, Kobori S, Takeda H, Higashi T, Sato Y, Sasahara T, Yano T, Kasho M, Anami Y, Shichiri M. Beta-migrating very low density lipoproteins induce foam cell formation in mouse mesangial cells. Atherosclerosis 1995; 114:123-32. [PMID: 7605371 DOI: 10.1016/0021-9150(94)05476-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
To elucidate whether beta-migrating very low density lipoproteins (beta-VLDL) induce foam cell formation in mesangial cells or not, surface binding and foam cell formation with beta-VLDL were studied in mouse mesangial cells. Specific binding kinetics for beta-VLDL and low density lipoproteins (LDL) on the mesangial cells were observed with Kd = 3.8 and 13.7 micrograms/ml, and Bmax = 65.9 and 71.9 ng/ml cell protein at 4 degrees C, respectively. The binding of beta-VLDL was inhibited by excess amounts of LDL or beta-VLDL, but not by acetyl-low density lipoproteins. Ligand blotting using beta-VLDL or LDL and immunoblotting using anti-human LDL receptor monoclonal antibody detected the same apparent single protein (approx. 130 kDa). Incorporation of [14C]oleate into cholesteryl ester in mouse mesangial cells was enhanced by beta-VLDL to 3-fold higher than that by LDL, and it was inhibited by chloroquine or anti-human LDL receptor monoclonal antibody. The light microscopic findings also demonstrated that cholesteryl ester deposition increased in these cells incubated with beta-VLDL, but not with LDL. In conclusion, beta-VLDL was specifically taken up by receptor-mediated endocytosis in mouse mesangial cells through LDL receptors, resulting in foam cell formation.
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Affiliation(s)
- T Nishikawa
- Department of Metabolic Medicine, Kumamoto University School of Medicine, Japan
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