Lipid droplet (LD) accumulation is a now well-recognised hallmark of cancer. However, the significance of LD accumulation in colorectal cancer (CRC) biology is incompletely understood under ...chemotherapeutic conditions. Since drug resistance is a major obstacle to treatment success, we sought to determine the contribution of LD accumulation to chemotherapy resistance in CRC. Here we show that LD content of CRC cells positively correlates with the expression of lysophosphatidylcholine acyltransferase 2 (LPCAT2), an LD-localised enzyme supporting phosphatidylcholine synthesis. We also demonstrate that LD accumulation drives cell-death resistance to 5-fluorouracil and oxaliplatin treatments both in vitro and in vivo. Mechanistically, LD accumulation impairs caspase cascade activation and ER stress responses. Notably, droplet accumulation is associated with a reduction in immunogenic cell death and CD8
T cell infiltration in mouse tumour grafts and metastatic tumours of CRC patients. Collectively our findings highlight LPCAT2-mediated LD accumulation as a druggable mechanism to restore CRC cell sensitivity.
Despite recent in vivo data demonstrating that high-fat diet (HFD)-induced obesity leads to major perturbations in murine hematopoietic stem cells (HSC), the direct role of a HFD is not yet ...completely understood. Here, we investigate the direct impact of a short-term HFD on HSC and hematopoiesis in C57BL/6J mice compared with standard diet-fed mice. We detect a loss of half of the most primitive HSC in the bone marrow (BM) cells of HFD-fed mice, which exhibit lower hematopoietic reconstitution potential after transplantation. Impaired maintenance of HSC is due to reduced dormancy after HFD feeding. We discover that a HFD disrupts the TGF-β receptor within lipid rafts, associated to impaired Smad2/3-dependent TGF-β signaling, as the main molecular mechanism of action. Finally, injecting HFD-fed mice with recombinant TGF-β1 avoids the loss of HSC and alteration of the BM's ability to recover, underscoring the fact that a HFD affects TGF-β signaling on HSC.
Scope
Omega‐3 fatty acids (O3FAs) and resveratrol (RSV) are known to be beneficial for certain eye diseases, such as age‐related macular degeneration (AMD). Neovascular AMD is characterized by ...abnormal blood vessel formation due to the excessive synthesis of vascular endothelial growth factor (VEGF) by retinal pigment epithelium (RPE) cells. The study investigates whether a formulation based on eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and RSV is capable of counteracting VEGF‐A secretion, and elucidates the molecular mechanism.
Methods and results
The study finds, using ELISA, that O3FAs/RSV reduces VEGF‐A secretion in human RPE cells. This phenomenon is related to the increased interaction between VEGF‐receptor 2 (VEGF‐R2) and caveolin‐1 (CAV‐1), a protein of detergent‐resistant membranes (DRMs), as determined by co‐immunoprecipitation and proximity ligation assay. Using microscale thermophoresis, the study confirms that O3FAs/RSV causes a high‐affinity interaction. Isolation and analysis of DRMs reveal that this interaction is concomitant with VEGF‐R2 relocalization in DRMs. The depletion of DRMs by a cholesterol‐chelating agent blocks the VEGF‐R2/CAV‐1 interaction and EPA/DHA/RSV‐mediated impairment of VEGF production.
Conclusion
This specific interaction can provide a new strategy for countering VEGF‐A production in human RPE cells and, consequently, reducing neovascularization in AMD. Further preclinical studies involving O3FAs and polyphenols are warranted.
Schematic illustration of the proposed mechanisms for omega‐3 fatty acid (O3FA)/resveratrol (RSV) combination on the vascular endothelial growth factor (VEGF) receptor 2 (VEGF‐R2) subcellular localization and VEGF‐A secretion. O3FA/RSV combination induces a relocalization of VEGF‐R2 in lipid rafts, where it interacts with CAV‐1. It is then inactive, inhibiting the cellular signaling pathways that enable VEGF‐A synthesis and secretion.
Background
Circulating endotoxins could result from bacterial digestive translocation during sepsis, thus contributing to uncontrolled systemic inflammation, leading in turn to organ dysfunction. We ...addressed this issue in the setting of severe pneumococcal pneumonia.
Methods
Endotoxemia was measured in a clinically relevant rabbit model of ventilated pneumococcal pneumonia and in 110 patients with bacteraemic pneumonia, using a patented mass spectrometry (LC–MS/MS) method for detection of 3‐OH fatty acids (C10, C12, C14, C16 and C18), which are molecules bound to the lipid A motif of LPS.
Results
Whereas higher levels of systemic inflammation and organ dysfunctions were found, there was no significant difference in lipopolysaccharide concentrations when infected rabbits were compared to non‐infected ones, or when patients were compared to healthy volunteers.
Conclusions
Seemingly, endotoxins do not drive the overwhelming inflammation associated with severe forms of pneumococcal pneumonia.
Quantitation of plasma lipopolysaccharides (LPSs) might be used to document Gram-negative bacterial infection. In the present work, LPS-derived 3-hydroxymyristate was extracted from plasma samples ...with an organic solvent, separated by reversed phase HPLC, and quantitated by MS/MS. This mass assay was combined with the limulus amebocyte lysate (LAL) bioassay to monitor neutralization of LPS activity in biological samples. The described HPLC/MS/MS method is a reliable, practical, accurate, and sensitive tool to quantitate LPS. The combination of the LAL and HPLC/MS/MS analyses provided new evidence for the intrinsic capacity of plasma lipoproteins and phospholipid transfer protein to neutralize the activity of LPS. In a subset of patients with systemic inflammatory response syndrome, with documented infection but with a negative plasma LAL test, significant amounts of LPS were measured by the HPLC/MS/MS method. Patients with the highest plasma LPS concentration were more severely ill. HPLC/MS/MS is a relevant method to quantitate endotoxin in a sample, to assess the efficacy of LPS neutralization, and to evaluate the proinflammatory potential of LPS in vivo.
The ability of oxysterols (7-ketocholesterol, 7β-hydroxycholesterol) to trigger a mode of cell death by apoptosis involving GSK-3 and caspase-3 activation is independent of the increase in the Ca2+ ...level and of their accumulation in lipid raft microdomains. Noteworthy, oxysterol-induced apoptosis was counteracted by α-tocopherol but not by ellagic acid and resveratrol. 27-hydroxycholesterol, which does not induce cell death, accumulates in lipid rafts.
There is some evidence that oxidized derivatives of cholesterol, 7-ketocholesterol (7KC) and 7β-hydroxycholesterol (7βOHC), are increased in the plasma of patients with neurodegenerative diseases associated with demyelinization of the central nervous system (CNS). It was therefore of interest to investigate the effects of these oxysterols on oligodendrocytes, the myelin-forming cells in the CNS. To this end, 158N murine oligodendrocytes were treated with 7KC or 7βOHC inducing an apoptotic mode of cell death characterized by condensation/fragmentation of the nuclei, dephosphorylation of Akt and GSK3, mitochondrial depolarization involving Mcl-1, and caspase-3 activation. In contrast, under treatment with 27-hydroxycholesterol (27OHC), no cell death was observed. When the cells were stained with Fura-2, no significant Ca2+ rise was found with the different oxysterols, whereas strong signals were detected with ionomycin used as positive control. At concentrations which induced apoptosis, 7KC but not 7βOHC accumulated in lipid rafts. Although not cytotoxic, 27OHC was mainly detected in lipid rafts. It is noteworthy that α-tocopherol (but not ellagic acid and resveratrol) was able to counteract 7KC- and 7βOHC-induced apoptosis and to decrease the accumulation of 7KC and 27OHC in lipid rafts. Thus, in 158N cells, the ability of oxysterols to trigger a mode of cell death by apoptosis involving GSK-3 and caspase-3 activation is independent of the increase in the Ca2+ level and of their accumulation in lipid raft microdomains.
Imeglimin is the first in a new class of oral glucose-lowering agents currently in phase 2b development. Although imeglimin improves insulin sensitivity in humans, the molecular mechanisms are ...unknown. This study used a model of 16-week high-fat, high-sucrose diet (HFHSD) mice to characterize its antidiabetic effects. Six-week imeglimin treatment significantly decreased glycemia, restored normal glucose tolerance, and improved insulin sensitivity without modifying organs, body weights, and food intake. This was associated with an increase in insulin-stimulated protein kinase B phosphorylation in the liver and muscle. In liver mitochondria, imeglimin redirects substrate flows in favor of complex II, as illustrated by increased respiration with succinate and by the restoration of respiration with glutamate/malate back to control levels. In addition, imeglimin inhibits complex I and restores complex III activities, suggesting an increase in fatty acid oxidation, which is supported by an increase in hepatic 3-hydroxyacetyl-CoA dehydrogenase activity and acylcarnitine profile and the reduction of liver steatosis. Imeglimin also reduces reactive oxygen species production and increases mitochondrial DNA. Finally, imeglimin effects on mitochondrial phospholipid composition could participate in the benefit of imeglimin on mitochondrial function. In conclusion, imeglimin normalizes glucose tolerance and insulin sensitivity by preserving mitochondrial function from oxidative stress and favoring lipid oxidation in liver of HFHSD mice.
Glucagon-like peptide 1 (GLP-1) is a hormone released from enteroendocrine L cells. Although first described as a glucoregulatory incretin hormone, GLP-1 also suppresses inflammation and promotes ...mucosal integrity. Here, we demonstrate that plasma GLP-1 levels are rapidly increased by lipopolysaccharide (LPS) administration in mice via a Toll-like receptor 4 (TLR4)-dependent mechanism. Experimental manipulation of gut barrier integrity after dextran sodium sulfate treatment, or via ischemia/reperfusion experiments in mice, triggered a rapid rise in circulating GLP-1. This phenomenon was detected prior to measurable changes in inflammatory status and plasma cytokine and LPS levels. In human subjects, LPS administration also induced GLP-1 secretion. Furthermore, GLP-1 levels were rapidly increased following the induction of ischemia in the human intestine. These findings expand traditional concepts of enteroendocrine L cell biology to encompass the sensing of inflammatory stimuli and compromised mucosal integrity, linking glucagon-like peptide secretion to gut inflammation.
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•LPS induce GLP-1 secretion from L cells through a TLR4-dependent mechanism•Gut ischemic injury is coupled to immediate GLP-1 secretion in mice and humans•L cells are mucosal sensors of LPS after gut injury•GLP-1 secretion is closely related to gut inflammation
Lebrun et al. demonstrate that enteroendocrine L cells sense lipopolysaccharides (pro-inflammatory bacterial compounds) after gut injury and respond by secreting glucagon-like peptide 1. These findings expand concepts of L cell function to include roles as both a nutrient and pathogen sensor, linking glucagon-like peptide secretion to gut inflammation.
To assess whether, in type 2 diabetic (T2D) patients, lipidomic abnormalities in high density lipoproteins (HDL) are associated with impaired cholesterol efflux capacity and anti-inflammatory effect, ...two pro-atherogenic abnormalities.
This is a secondary analysis of the Lira-NAFLD study, including 20 T2D patients at T0 and 25 control subjects. Using liquid chromatography/tandem mass spectrometry, we quantified 110 species of the main HDL phospholipids and sphingolipids. Cholesterol efflux capacity was measured on THP-1 macrophages. The anti-inflammatory effect of HDL was measured as their ability to inhibit the TNFα-induced expression of Vascular Cell Adhesion Molecule-1 (VCAM-1) and Intercellular Cell Adhesion Molecule-1 (ICAM-1) on Human Vascular Endothelial Cells (HUVEC).
The cholesterol-to-triglyceride ratio was decreased in HDL from T2D patients compared to controls (-46%, P=0.00008). As expressed relative to apolipoprotein AI, the amounts of phosphatidylcholines, sphingomyelins and sphingosine-1-phosphate were similar in HDL from T2D patients and controls. Phosphatidylethanolamine-based plasmalogens and ceramides were respectively 27% (P=0.038) and 24% (P=0.053) lower in HDL from T2D patients than in HDL from controls, whereas phosphatidylethanolamines were 41% higher (P=0.026). Cholesterol efflux capacity of apoB-depleted plasma was similar in T2D patients and controls (36.2±4.3 vs 35.5±2.8%, P=0.59). The ability of HDL to inhibit the TNFα-induced expression of both VCAM-1 and ICAM-1 at the surface of HUVEC was similar in T2D patients and controls (-70.6±16.5 vs -63.5±18.7%, P=0.14 and -62.1±13.2 vs -54.7±17.7%, P=0.16, respectively).
Despite lipidomic abnormalities, the cholesterol efflux and anti-inflammatory capacities of HDL are preserved in T2D patients.
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