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Neale D Ridgway – 1st expert on this subject based on the ideXlab platform
chinese hamster ovary cells overexpressing the oxysterol binding protein osbp display enhanced synthesis of sphingomyelin in response to 25 HydroxycholesterolJournal of Lipid Research, 1999Co-Authors: Thomas A Lagace, David M Byers, Harold W Cook, Neale D RidgwayAbstract:
Hydroxycholesterol negatively regulates cho- lesterol synthesis and activates cholesterol esterification in a variety of cultured cells. Concurrent with these effects, 25– Hydroxycholesterol also stimulates the synthesis of sphingo- myelin in Chinese hamster ovary (CHO)-K1 cells. The role of oxysterol binding protein (OSBP), a high affinity recep- tor for 25–Hydroxycholesterol, in activation of SM synthesis was assessed by overexpression in CHO-K1 cells. When compared to mock transfected controls, three CHO-K1 clones overexpressing OSBP by 10- to 15-fold displayed a 2- to 3-fold enhancement of ( 3 H)serine incorporation into sphingomyelin when treated with 25–Hydroxycholesterol. Closer examination of one of these clones (CHO-OSBP cells) revealed a . 8.5-fold stimulation of sphingomyelin synthesis after a 6-h treatment with 25–Hydroxycholesterol compared to 3.5-fold in controls, slightly higher basal levels of sphingomyelin synthesis, and a more rapid response to 25–Hydroxycholesterol. ( 3 H)serine incorporation into phos- phatidylserine, phosphatidylethanolamine, ceramide, or glucosylceramide was affected by , 15%. Synthesis of sphin- gomyelin from exogenous ( 3 H)sphinganine-labeled cera- mide was enhanced in overexpressing cells treated with 25– Hydroxycholesterol. However, in vitro activities of sphinganine N -acyltransferase, sphingomyelin synthase, and serine palm- itoyltransferase were not affected by OSBP overexpression or 25–Hydroxycholesterol. Overexpression of OSBP or 25– Hydroxycholesterol did not significantly affect the ceramide content of Golgi-enriched fractions from control or overex- pressing cells. However, diglyceride mass was reduced in Golgi-enriched fractions from overexpressing cells and by treatment with 25–Hydroxycholesterol. Results from over- expressing cells show that OSBP potentiates the stimulatory effects of 25–Hydroxycholesterol on sphingomyelin synthe- sis. 25–Hydroxycholesterol promotes translocation of OSBP to the Golgi apparatus where it appears to stimulate conver- sion of ceramide to sphingomyelin.— Lagace, T. A., D. M. Byers, H. W. Cook, and N. D. Ridgway. Chinese hamster ovary cells overexpressing the oxysterol binding protein (OSBP) display enhanced synthesis of sphingomyelin in re- sponse to 25–Hydroxycholesterol. J. Lipid Res. 1999. 40: 109- 116.
cholesterol regulates oxysterol binding protein osbp phosphorylation and golgi localization in chinese hamster ovary cells correlation with stimulation of sphingomyelin synthesis by 25 HydroxycholesterolBiochemical Journal, 1998Co-Authors: Margo K Storey, Harold W Cook, David M Byers, Neale D RidgwayAbstract:
: Sphingomyelin (SM) and cholesterol content is positively correlated in cellular membranes, and in several pathological and experimental conditions there is evidence for coregulation. The potential role of oxysterols and oxysterol binding protein (OSBP) in mediating the coregulation of cholesterol and SM was examined using Chinese hamster ovary (CHO) and cholesterol auxotrophic, sterol regulatory defective (SRD) 6 cells. SRD 6 cells grown in the presence or absence of cholesterol for 24 h displayed a 30-50% reduction in SM synthesis compared with control CHO 7 cells. SM synthesis in CHO 7 and cholesterol-supplemented SRD 6 cells was stimulated 2-fold by 25–Hydroxycholesterol, but cholesterol-starved SRD 6 cells were unresponsive. Basal and 25–Hydroxycholesterol-stimulated SM synthesis was also inhibited in lovastatin-treated wild-type CHO-K1 cells. Lack of 25–Hydroxycholesterol activation of SM synthesis in cholesterol-starved SRD 6 and lovastatin-treated CHO-K1 cells was correlated with dephosphorylation of OSBP. In SRD 6 cells, this was evident after 12 h of cholesterol depletion, it occurred equally at all phosphorylation sites and was exacerbated by 25–Hydroxycholesterol. Unlike CHO 7 cells, where OSBP was observed in small vesicles and the cytoplasm, OSBP in cholesterol-starved SRD 6 cells was constitutively localized in the Golgi apparatus. Supplementation with non-lipoprotein cholesterol promoted redistribution to vesicles and the cytoplasm. Similarly, OSBP in CHO-K1 cells grown in delipidated serum was predominantly in the Golgi apparatus. Low-density lipoprotein (LDL) supplementation of CHO-K1 cells caused the redistribution of OSBP to the cytoplasm and small vesicles, and this effect was blocked by pharmacological agents ?3-beta-[2-(diethylamino)ethoxy]androst-5-en-17-one and progesterone?, which inhibited LDL cholesterol efflux from lysosomes. The results showed that localization of OSBP between the Golgi apparatus and a cytoplasmic/vesicular compartment was responsive to changes in cholesterol content and trafficking. In cholesterol depleted SRD 6 cells, this was accompanied by dephosphorylation of OSBP and attenuation of 25–Hydroxycholesterol activation of SM synthesis.
25 Hydroxycholesterol stimulates sphingomyelin synthesis in chinese hamster ovary cellsJournal of Lipid Research, 1995Co-Authors: Neale D RidgwayAbstract:
In several experimental and pathological conditions the cellular concentrations of cholesterol and sphingomyelin (SM) change coordinately. In an effort to identify factors medi- ating co-regulation, a class of suppressors of cholesterol synthe- sis, generically termed oxysterols, were tested for effects on sphingolipid synthesis in Chinese hamster ovary (CHO) cells. 25-Hydroxycholestero1 was found to stimulate (3H)serine, (l-SHIpalmitate, and (methyl-3H)choline incorporation into sphingomyelin 2- to 3-fold and increase sphingomyelin mass significantly, but did not influence synthesis of other major phos- pholipids. Maximal labeling of sphingomyelin by (SHIserine was observed 4-6 h after oxysterol addition, and coincided with inhi- bition of transcription of sterol-regulated genes and activation of cholesteryl ester synthesis. 25-Hydroxycholesterpl dose-response curves for activation of sphingomyelin synthesis, suppression of sterol-regulated transcription, and activation of cholesteryl ester synthesis were also similar. Stimulation of SM and glucosylcera- mide synthesis was observed only with 25–Hydroxycholesterol; other oxysterols and cholesterol were ineffective or inhibitory. The effects of 25–Hydroxycholesterol on sphingolipid synthesis could not be reproduced by low density lipoprotein (LDL), whole serum, or non-lipoprotein cholesterol in the medium, and stimulation by 25-hydroxycholestero1 was evident irrespective of a cholesterol source in the medium. 25-Hydroxycholestero1- treated CHO ds displayed enhanced conversion of (3H)sphinpanine- labeled ceramide into sphingomyelin. Sphingomyelin synthesis from N-hexanoyl (3-3H)ceramide and N-hexanoyl (3-3H)di- hydroceramide was also increased significantly. Consistent with enhanced ceramide conversion to sphingomyelin, ceramide mass was reduced by 20-4076 in 25-hydroxycholesteroI-treatment. However, in vitro activity of sphingomyelin synthase (assayed with short-chain ceramide) was not increased in membranes from oxysterol-treated cells. Stimulation of sphingolipid synthesis by 25–Hydroxycholesterol is temporally related to effects of this oxysterol on cholesterol metabolism, and is the result of enhanced conversion of ceramide to SM.-Ridgway, N. D. 25-Hydroxycholestero1 stimulates sphingomyelin synthesis in Chinese hamster ovary cells. J Lipid Res. 1995. 36: 1345-1358. Supplementary key sphingomyelin ceramide oxysterols sphingo- myelin synthase
James C Hutson – 2nd expert on this subject based on the ideXlab platform
Testosterone Regulates 25–Hydroxycholesterol Production in Testicular MacrophagesBiology of Reproduction, 2002Co-Authors: Yevgenia O Lukyanenko, Jaujiin Chen, James C HutsonAbstract:
Recently, we found that testicular macrophages produce 25–Hydroxycholesterol (25-HC) and express 25-hydroxylase, the enzyme that converts cholesterol to 25-HC. In addition, 25-HC may be an important paracrine factor mediating the known interactions between macrophages and neighboring Leydig cells, because it is efficiently converted to testosterone by Leydig cells. The purpose of the present study was to determine if testosterone can regulate the production of 25-HC in rat testicular macrophages, representing a potential negative-feedback loop from Leydig cells. We found that expression of 25-hydroxylase mRNA and production of 25-HC by cultured testicular macrophages were significantly inhibited by testosterone at 10 μg/ml. This dose of testosterone did not have an effect on cell viability and did not change the rate of mRNA degradation in the presence of actinomycin D. These studies indicate that production of 25-HC is negatively regulated by testosterone, which may be representative of a paracrine negative-feedback loop.
25–Hydroxycholesterol Is Produced by Testicular Macrophages During the Early Postnatal Period and Influences Differentiation of Leydig Cells In VitroBiology of Reproduction, 2002Co-Authors: Jaujiin Chen, Yevgenia O Lukyanenko, James C HutsonAbstract:
Leydig cells develop inappropriately in animals lacking testicular macrophages. We have recently found that macrophages from adult animals produce 25–Hydroxycholesterol, an oxysterol involved in the differentiation of hepatocytes and keratinocytes. Therefore, we hypothesized that testicular macrophages also produce 25–Hydroxycholesterol during the early postnatal period and that this oxysterol plays a role in the differentiation of Leydig cells. We assessed the production of 25–Hydroxycholesterol and 25-hydroxylase mRNA by cultured testicular macrophages from rats at 10, 20, and 40 days of age. We also tested the long-term effects of 25–Hydroxycholesterol on basal and LH-stimulated testosterone production, and 3β-hydroxysteroid dehydrogenase activity as end points of Leydig cell differentiation in vitro. We found that testicular macrophages from animals at all ages produced both 25–Hydroxycholesterol and 25-hydroxylase mRNA, with macrophages from 10-day-old animals having the highest steady-state levels of message. We also found that chronic exposure of Leydig cells to 25–Hydroxycholesterol increased basal production of testosterone but decreased LH-stimulated steroidogenesis at all ages. Finally, 25–Hydroxycholesterol increased 3β-hydroxysteroid dehydrogenase activity in both progenitor and immature Leydig cells. These findings support the hypothesis that testicular macrophages play an important role in the differentiation of Leydig cells through the secretion of 25–Hydroxycholesterol.
production of 25 Hydroxycholesterol by testicular macrophages and its effects on leydig cellsBiology of Reproduction, 2001Co-Authors: Yevgenia O Lukyanenko, Jaujiin Chen, James C HutsonAbstract:
Abstract Testicular macrophages secrete 25–Hydroxycholesterol, which can be converted to testosterone by neighboring Leydig cells. The purposes of the present studies were to determine the mode of production of this oxysterol and its long-term effects on Leydig cells. Because oxysterols are produced both enzymatically and by auto-oxidation, we first determined if testicular macrophages possess cholesterol 25-hydroxylase mRNA and/or if macrophage-secreted products oxidize cholesterol extracellularly. Rat testicular macrophages had 25-hydroxylase mRNA and converted 14C-cholesterol to 14C-25–Hydroxycholesterol; however, radiolabeled cholesterol was not converted to 25–Hydroxycholesterol when incubated with medium previously exposed to testicular macrophages. Exposure of Leydig cells to 10 μg/ml of 25–Hydroxycholesterol, a dose within the range known to result in high basal production of testosterone when tested from 1 to 6 h, completely abolished LH responsiveness after 2 days of treatment. Because 25-hydrox…
David W Russell – 3rd expert on this subject based on the ideXlab platform
25 Hydroxycholesterol suppresses interleukin 1 driven inflammation downstream of type i interferonScience, 2014Co-Authors: Andrea Reboldi, David W Russell, Jeffrey G Mcdonald, Guosheng Liang, Eric V Dang, Jason G CysterAbstract:
Type I interferon (IFN) protects against viruses, yet it also has a poorly understood suppressive influence on inflammation. Here, we report that activated mouse macrophages lacking the IFN-stimulated gene cholesterol 25-hydroxylase ( Ch25h ) and that are unable to produce the oxysterol 25–Hydroxycholesterol (25-HC) overproduce inflammatory interleukin-1 (IL-1) family cytokines. 25-HC acts by antagonizing sterol response element–binding protein (SREBP) processing to reduce Il1b transcription and to broadly repress IL-1–activating inflammasomes. In accord with these dual actions of 25-HC, Ch25h-deficient mice exhibit increased sensitivity to septic shock, exacerbated experimental autoimmune encephalomyelitis, and a stronger ability to repress bacterial growth. These findings identify an oxysterol, 25-HC, as a critical mediator in the negative-feedback pathway of IFN signaling on IL-1 family cytokine production and inflammasome activity.
25 Hydroxycholesterol secreted by macrophages in response to toll like receptor activation suppresses immunoglobulin a productionProceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: David R Bauman, Andrew Bitmansour, Jeffrey G Mcdonald, Bonne M Thompson, Guosheng Liang, David W RussellAbstract:
25–Hydroxycholesterol is produced in mammalian tissues. The function of this oxysterol is unknown. Here we describe a central role for 25–Hydroxycholesterol in regulating the immune system. In initial experiments, we found that stimulation of macrophage Toll-like receptors (TLR) induced expression of cholesterol 25-hydroxylase and the synthesis of 25–Hydroxycholesterol. Treatment of naive B cells with nanomolar concentrations of 25–Hydroxycholesterol suppressed IL-2-mediated stimulation of B cell proliferation, repressed activation-induced cytidine deaminase (AID) expression, and blocked class switch recombination, leading to markedly decreased IgA production. Consistent with these findings, deletion of the mouse cholesterol 25-hydroxylase gene caused an increase in serum IgA. Conversely, inactivation of the CYP7B1 oxysterol 7α-hydroxylase, which degrades 25–Hydroxycholesterol, decreased serum IgA. The suppression of IgA class switching in B cells by a macrophage-derived sterol in response to TLR activation provides a mechanism for local and systemic negative regulation of the adaptive immune response by the innate immune system.