Project description:Cholesterol is the precursor of all steroids, but how cholesterol flux is controlled in steroidogenic tissues is poorly understood. The cholesterol exporter ABCG1 is an essential component of the reverse cholesterol pathway and its systemic inactivation results in neutral lipid redistribution to macrophages. However, the function of ABCG1 in steroidogenic organs is not explored. To model this question, we inactivated the ortholog Abcg1 gene in the mouse adrenal cortex. Abcg1 disruption led to an adrenal-specific increase in transcripts involved in cholesterol uptake and de novo synthesis, and to an 80% increase in corticosterone production. Importantly, this phenotype was not recapitulated by inactivation of the cholesterol exporter Abca1. The absence of any change in lipid profile suggested that adrenal Abcg1 is not involved in cholesterol export to a clinically relevant extent.
Project description:ATP binding cassette subfamily member 1 (ABCA1) and G1 (ABCG1) are cholesterol efflux transporter to prevent excess intracellular cholesterol accumulation. We here report the deletion of Abca1 and Abcg1 results in the significant increased expression of Cd38, a multi-faceted ectoenzyme with NADase activity.
Project description:Hormones produced by the adrenal cortex are absolutely essential for numerous processes in living animals. Our research group investigated to what extend the central regulators of deprived oxygen, hypoxia inducible factors (HIFs), contribute to this steroidogenesis. For this, we developed a set of new transgenic mouse lines displaying modified HIF1α and HIF2α levels in cortical cells and revealed that HIF1α exclusively regulates the transcription of a majority of enzymes responsible for the production of glucocorticoids and mineralocorticoids as well as a consequent inflection of cytokines in circulation. These novel tools will be helpful to understand how sustained and chronic changes in adrenocortical hormones can impact during health and disease.
Project description:The Wnt pathway, which controls crucial steps of the development and differentiation programs, has been proposed to influence lipid storage and homeostasis. In this paper, using an unbiased strategy based on high content genome-wide RNAi screens that monitored lipid distribution and amounts, we find that Wnt3a regulates cellular cholesterol. We show that Wnt3a stimulates the production of lipid droplets, and that this stimulation strictly depends on endocytosed, LDL-derived cholesterol and on functional early and late endosomes. We also show that Wnt signaling itself controls cholesterol endocytosis and flux along the endosomal pathway, which in turn modulates cellular lipid homeostasis. These results underscore the importance of endosome functions for LD formation and reveal a previously unknown cellular program controlling lipid storage and endosome transport under the control of Wnt signaling.
Project description:Excess cholesterol accumulation in lesional macrophages elicits complex responses in atherosclerosis. Epsins, a family of endocytic adaptors, fuel the progression of atherosclerosis; however, the underlying mechanism and therapeutic potential of targeting Epsins remains unknown. In this study, we determined the role of Epsins in macrophage-mediated metabolic regulation. We then developed an innovative method to therapeutically-target macrophage Epsins with specially-designed S2P-conjugated lipid nanoparticles (NPs), which encapsulate small interfering RNAs to suppress Epsins.Our findings suggest that targeting Epsins in lesional macrophages may offer therapeutic benefits for advanced atherosclerosis by reducing CD36-mediated lipid uptake and increasing ABCG1-mediated cholesterol efflux.
Project description:Excess cholesterol accumulation in lesional macrophages elicits complex responses in atherosclerosis. Epsins, a family of endocytic adaptors, fuel the progression of atherosclerosis; however, the underlying mechanism and therapeutic potential of targeting Epsins remains unknown. In this study, we determined the role of Epsins in macrophage-mediated metabolic regulation. We then developed an innovative method to therapeutically-target macrophage Epsins with specially-designed S2P-conjugated lipid nanoparticles (NPs), which encapsulate small interfering RNAs to suppress Epsins.Our findings suggest that targeting Epsins in lesional macrophages may offer therapeutic benefits for advanced atherosclerosis by reducing CD36-mediated lipid uptake and increasing ABCG1-mediated cholesterol efflux.
Project description:We hypothesize that changes in adrenal gene expression mediate the increased plasma corticosterone and steroidogenesis in rat pups exposed to hypoxia from birth. Keywords: effects of hypoxia on adrenal steroidogenesis in the neonatal rat
Project description:Transcriptional profiling of cytokines and its receptors in lungs from 8 month old chow-fed wild-type and ABCG1-/- mice Keywords: genotype comparison; inflammatory mediators 4 individual mice per group; RNA from inferior left lobe; WT vs. ABCG1-/-
Project description:Cellular lipid requirements are achieved through a combination of biosynthesis and import programs. Using isotope tracer analysis, we show that type I interferon (IFN) signaling rapidly shifts the balance of these programs by decreasing synthesis and increasing import of cholesterol and long chain fatty acids. Genetically enforcing this metabolic shift in macrophages is sufficient to render mice resistant to viral challenge, demonstrating the importance of reprogramming the balance of these two metabolic pathways in vivo. Unexpectedly, mechanistic studies reveal that limiting flux through the cholesterol biosynthetic pathway spontaneously engages a type I IFN response in a STING-dependent manner. The upregulation of type I IFNs was traced to a decrease in the pool size of synthesized cholesterol, and could be inhibited by replenishing cells with free cholesterol. Taken together, these studies delineate a metabolic-inflammatory circuit that links perturbations in cholesterol biosynthesis with activation of innate immunity. shRNA to SREBF1 (shSREBP1) or SREBF2 (shSREBP2) were stably introduced via 3rd generation lentivirus into human THP1 monocytic cells under puromycin selection. Non-targeting shRNA scramble was used for a control (shControl). shControl, shSREBP1 and shSREBP2 modified cell types were analyzed by RNA-seq in duplicate.