Carbon dioxide regulates cholesterol levels through SREBP2
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE196294 | GEO | 2023/10/06
REPOSITORIES: GEO
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Project description:Cholesterol homeostasis plays a central role in disease pathogenesis in chronic disorders such as cardiovascular and kidney diseases. The transcription factor SREBP2 is the main regulator of cholesterol metabolism and is central to the mechanism of action of lipid lowering drugs, such as statins, that are responsible for the largest overall reduction in cardiovascular risk and mortality in humans with atherosclerotic cardiovascular disease. Recently, SREBP2 has been implicated in both the innate and adaptive immune responses by upregulation of cholesterol flux or via direct transcriptional activation of pro-inflammatory genes in leukocytes. Here, we investigate the role of SREBP2 in endothelial cells (ECs), since ECs are at the interface of circulating lipids with tissues and are activated in response to damage and inflammation. The loss of SREBP2 in cultured human ECs results in significant alterations of the transcriptional response to inflammatory cytokines whereas SREBF2 knockdown inhibits the transcription and secretion of pro-inflammatory chemokines but amplifies type I interferon response genes. Furthermore, we show that SREBP2 regulates chemokine expression not through enhancement of endogenous cholesterol synthesis or lipoprotein uptake, but partially through direct transcriptional activation. Chromatin immunoprecipitation sequencing (ChIP-seq) of endogenous SREBP2 reveals the SREBP2 bound to the promoter regions of classical response genes as well as two non-classical sterol responsive genes involved in immune modulation, BHLHE40 and KLF6. Overexpression of SREBP2 upregulated both BHLHE40 and KLF6 transcripts independent of inflammatory stress and the transcription of these genes were found to be sensitive to cellular cholesterol levels. Of these two targets, we found that KLF6 was responsible for the amplification of chemokine expression highlighting a tight relationship between cholesterol homeostasis and inflammatory phenotypes in ECs.
2023-08-21 | GSE223094 | GEO
Project description:In our work, we uncovered a critical role for cholesterol homeostasis in terminal erythropoiesis. The master transcriptional factor GATA1 binds to Sterol-regulatory element binding protein 2 (SREBP2) to downregulate cholesterol biosynthesis, leading to a gradual reduction in intracellular cholesterol levels. To reveal genetic interactions and epistatic relations between GATA1 and SREBP2 on depth at the whole genome level, we performed RNA sequencing to analyze the gene expression profiles change between treated with Vehicle or β-estradiol in overexpressing active SREBP2 G1E-ER4 cells.
2022-02-08 | GSE184002 | GEO
Project description:Scope: Consumption of industrial trans fatty acids unfavourably alters plasma cholesterol and has been linked to NAFLD. However, the mechanisms underlying these deleterious effects of trans fatty acids are unclear. Here, we aim to investigate the molecular mechanisms of action of industrial trans fatty acids. Methods & Results: Hepa1-6 hepatoma cells were incubated with elaidate, oleate, or palmitate. C57Bl/6 mice were fed diets rich in trans-unsaturated, cis-unsaturated or saturated fatty acids. Transcriptomics analysis of Hepa1-6 cells showed that elaidate but not oleate or palmitate induced expression of genes involved in cholesterol biosynthesis. Induction of cholesterogenesis by elaidate was mediated by increased SREBP2 and dependent on SCAP, yet independent of LXR and UBXD8. Elaidate decreased intracellular free cholesterol levels and repressed the anti-cholesterogenic effect of exogenous cholesterol. In mice, the trans-unsaturated diet increased the ratio of liver to gonadal fat mass, steatosis, hepatic cholesterol levels, ALT activity, and fibrosis markers, suggesting enhanced NAFLD, compared to the cis-unsaturated and saturated diets. Conclusion: Elaidate induces cholesterogenesis in vitro via activation of the SCAP-SREBP axis, likely by lowering intracellular free cholesterol and attenuating cholesterol-dependent repression of SCAP. This pathway potentially underlies the increase in liver cholesterol and NAFLD by industrial trans fatty acids.
2019-08-27 | GSE136271 | GEO
Project description:We found the genome-wide co-binding of QKI-5 and SREBP2. Notably, the genomic distribution analysis revealed that the co-binding events between QKI-5 and SREBP2 highly occurred at the regions of the promoter/transcription start site (TSS), where active transcription was taken place in a lens cell-specific manner, which was indicated by POL II binding events. Cellular pathway analysis of the genes whose promoters were co-bound by QKI-5, SREBP2, and POL II showed a significant enrichment of the SREBP2-medaited cholesterol biosynthesis pathway, and QKI depletion led to reduced co-occupancies of SREBP2 and POL II on the promoters of the genes involved in cholesterol biosynthesis. These data suggest QKI-5 as a potential transcription co-activator mediating SREBP2-dependent cholesterol biosynthesis in eye lens cells.
2021-01-29 | GSE144757 | GEO
Project description:Scope: Consumption of industrial trans fatty acids unfavourably alters plasma cholesterol and has been linked to NAFLD. However, the mechanisms underlying these deleterious effects of trans fatty acids are unclear. Here, we aim to investigate the molecular mechanisms of action of industrial trans fatty acids. Methods & Results: Hepa1-6 hepatoma cells were incubated with elaidate, oleate, or palmitate. C57Bl/6 mice were fed diets rich in trans-unsaturated, cis-unsaturated or saturated fatty acids. Transcriptomics analysis of Hepa1-6 cells showed that elaidate but not oleate or palmitate induced expression of genes involved in cholesterol biosynthesis. Induction of cholesterogenesis by elaidate was mediated by increased SREBP2 and dependent on SCAP, yet independent of LXR and UBXD8. Elaidate decreased intracellular free cholesterol levels and repressed the anti-cholesterogenic effect of exogenous cholesterol. In mice, the trans-unsaturated diet increased the ratio of liver to gonadal fat mass, steatosis, hepatic cholesterol levels, ALT activity, and fibrosis markers, suggesting enhanced NAFLD, compared to the cis-unsaturated and saturated diets. Conclusion: Elaidate induces cholesterogenesis in vitro via activation of the SCAP-SREBP axis, likely by lowering intracellular free cholesterol and attenuating cholesterol-dependent repression of SCAP. This pathway potentially underlies the increase in liver cholesterol and NAFLD by industrial trans fatty acids.
2019-08-27 | GSE136351 | GEO
Project description:Scope: Consumption of industrial trans fatty acids unfavourably alters plasma cholesterol and has been linked to NAFLD. However, the mechanisms underlying these deleterious effects of trans fatty acids are unclear. Here, we aim to investigate the molecular mechanisms of action of industrial trans fatty acids. Methods & Results: Hepa1-6 hepatoma cells were incubated with elaidate, oleate, or palmitate. C57Bl/6 mice were fed diets rich in trans-unsaturated, cis-unsaturated or saturated fatty acids. Transcriptomics analysis of Hepa1-6 cells showed that elaidate but not oleate or palmitate induced expression of genes involved in cholesterol biosynthesis. Induction of cholesterogenesis by elaidate was mediated by increased SREBP2 and dependent on SCAP, yet independent of LXR and UBXD8. Elaidate decreased intracellular free cholesterol levels and repressed the anti-cholesterogenic effect of exogenous cholesterol. In mice, the trans-unsaturated diet increased the ratio of liver to gonadal fat mass, steatosis, hepatic cholesterol levels, ALT activity, and fibrosis markers, suggesting enhanced NAFLD, compared to the cis-unsaturated and saturated diets. Conclusion: Elaidate induces cholesterogenesis in vitro via activation of the SCAP-SREBP axis, likely by lowering intracellular free cholesterol and attenuating cholesterol-dependent repression of SCAP. This pathway potentially underlies the increase in liver cholesterol and NAFLD by industrial trans fatty acids.
2019-08-27 | GSE136278 | GEO
Project description:Immunometabolism is a growing field that centers on a core paradigm: perturbations in metabolism alter a cell’s biological response in immunity and, likewise, inflammatory signals, such as cytokines and pathogens, can directly influence cellular metabolism. Although the carbons within cholesterol cannot be used for catabolic energy production, there is a growing appreciation that a similar relationship exists between cholesterol homeostasis and immunity. The majority of this literature is focused on cholesterol dynamics in the context of leukocyte immunobiology. However, the endothelium also plays an important role during the acute inflammatory response. Endothelial cells (ECs) rapidly respond to extrinsic signals, such as tissue damage or microbial infection, by upregulating factors to activate and recruit circulating leukocytes to the site of injury. Dysregulation or aberrant activation of ECs leads to disease, such as atherosclerosis. I studied the role of cholesterol and its master regulator, SREBP2, in the EC response to acute inflammatory stress. ECs treated with cytokines upregulated SREBP2 cleavage and classical cholesterol biosynthesis gene expression within the late phase of the acute inflammatory response. Furthermore, SREBP2 activation was dependent on NF-kB DNA binding and classical SCAP-SREBP2 processing. We used bacterial cytolysin probes to show that inflammatory stress significantly decreased accessible cholesterol, leading to dysfunctional sterol sensing and downstream SREBP2 cleavage. We also explored what role SREBP2 plays in the EC inflammatory response. Loss of SREBP2 in ECs treated with inflammatory cytokine altered EC phenotype, which was defined by decreased chemokine expression and increased type I inflammatory signaling. Interestingly, this effect on the EC inflammatory transcriptome could not be accounted by changes in cholesterol, but rather through SREBP2 binding to promoters of pro-inflammatory transcription factors. Preliminary results revealed that BHLHE40 and KLF6 are direct targets of SREBP2 and that loss of one of KLF6 could mimic the effect of SREBP2 knockdown on chemokine expression. This study is the first to provide an in-depth characterization of the relationship between SREBP2 and the endothelial acute inflammatory response.
2022-07-14 | GSE207919 | GEO
Project description:Metabolic reprogramming is well-appreciated to be able to control macrophage activation. However, it remains unknown whether the SREBPs-lipogenesis pathway is involved in macrophage alternative (or M2) activation. Here, we showed that IL4-induced M2 activation was coupled with increased SREBP2 maturation and activated cholesterol biosynthetic pathway, while the SREBP1-fatty acid biosynthesis pathway remained unaffected after IL4 stimulation. Genetic or pharmacologic blockade of SREBP2 maturation significantly inhibited IL4-induced M2 activation independent of cholesterol. Instead, cholesterol inhibited M2 activation most likely through its feedback regulation of SREBP2 maturation. Mechanically, the upregulation of SREBP2 maturation was dependent on the activation of upstream MTOR, and mature SREBP2 increased the expression of KAZALD1 and subsequently activated the IGF1 signaling to promote IL4-induced M2 activation. Consistently, myeloid-specific Scap deficiency markedly decreased the number of M2 macrophages in the lung and attenuated the HDM-induced allergic airway inflammation. Taken together, these findings highlight a critical role for cholesterol homeostatic regulator SREBP2 in M2 activation, which advances our understanding of the regulation of immunometabolism for M2 activation and points to new opportunities for therapeutic control of M2 activation and allergic airway inflammation.
2023-04-30 | GSE188356 | GEO
Project description:Macrophage cholesterol homeostasis is crucial for health and disease and has been linked to the lipid-peroxidizing enzyme arachidonate 15-lipoxygenase type B (ALOX15B), albeit molecular mechanisms remain obscure. We performed global transcriptome and immunofluorescence analysis in ALOX15B-silenced primary human macrophages and observed a reduction of nuclear sterol regulatory element-binding protein (SREBP) 2, the master transcription factor of cellular cholesterol biosynthesis. Consequently, SREBP2-target gene expression was reduced as were the sterol biosynthetic intermediates desmosterol and lathosterol as well as 25- and 27-hydroxycholesterol. Mechanistically, suppression of ALOX15B reduced lipid peroxidation in primary human macrophages and thereby attenuated activation of mitogen-activated protein kinase ERK1/2, which lowered SREBP2 abundance and activity. Low nuclear SREBP2 rendered both, ALOX15B-silenced and ERK1/2-inhibited macrophages refractory to SREBP2 activation upon blocking the NPC intracellular cholesterol transporter 1. These studies suggest a regulatory mechanism controlling macrophage cholesterol homeostasis based on ALOX15B-mediated lipid peroxidation and concomitant ERK1/2 activation.
2024-04-07 | GSE208160 | GEO
Project description:We found the genome-wide co-localization of Qki-5 and Srebp2. Notably, the genomic distribution analysis revealed that Qki-5 and Srebp2 highly co-occupied the regions of the promoter/transcription start site (TSS), where active transcription was taken place in a oligodendrocyte-specific manner, which was indicated by Pol II binding events. GO analysis of the genes whose promoters were co-bound by Qki-5, Srebp2, and Pol II showed a significant enrichment of the Srebp2-mediated cholesterol biosynthesis pathway, and Qki depletion led to reduced recruitment of Srebp2 and Pol II on the promoters of the genes involved in cholesterol biosynthesis. These data suggest Qki-5 as a potential transcription co-activator of Srebp2-mediated cholesterol biosynthesis in oligodendrocytes.
2021-05-10 | GSE144756 | GEO