CD36 coordinates NLRP3 inflammasome activation by facilitating the intracellular nucleation from soluble to particulate ligands in sterile inflammation

Particulate ligands including cholesterol crystals and amyloid fibrils induce NLRP3-dependent production of interleukin-1β (IL-1β) in atherosclerosis, Alzheimer's disease and diabetes. Soluble endogenous ligands including oxidized-LDL, amyloid-β and amylin peptides accumulate in these diseases. Here we identify a CD36-mediated endocytic pathway that coordinates the intracellular conversion of these soluble ligands to crystals or fibrils, resulting in lysosomal disruption and NLRP3-inflammasome activation. Consequently, macrophages lacking CD36 failed to elicit IL-1β production in response to these ligands and targeting CD36 in atherosclerotic mice reduced serum IL-1β and plaque cholesterol crystal accumulation. Collectively, these findings highlight the importance of CD36 in the accrual and nucleation of NLRP3 ligands from within the macrophage and position CD36 as a central regulator of inflammasome activation in sterile inflammation

RIPK1 gene variants associate with obesity in humans and can be therapeutically silenced to reduce obesity in mice

Obesity is a major public health burden worldwide and is characterized by chronic low-grade inflammation driven by the cooperation of the innate immune system and dysregulated metabolism in adipose tissue and other metabolic organs. Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) is a central regulator of inflammatory cell function that coordinates inflammation, apoptosis and necroptosis in response to inflammatory stimuli. Here we show that genetic polymorphisms near the human RIPK1 locus associate with increased RIPK1 gene expression and obesity. We show that one of these single nucleotide polymorphisms is within a binding site for E4BP4 and increases RIPK1 promoter activity and RIPK1 gene expression in adipose tissue. Therapeutic silencing of RIPK1 in vivo in a mouse model of diet-induced obesity dramatically reduces fat mass, total body weight and improves insulin sensitivity, while simultaneously reducing macrophage and promoting invariant natural killer T cell accumulation in adipose tissue. These findings demonstrate that RIPK1 is genetically associated with obesity, and reducing RIPK1 expression is a potential therapeutic approach to target obesity and related diseases

Maternal and Placental Antibody Responses in SARS-CoV-2 Vaccination and Natural Infection During Pregnancy.

BACKGROUND: As COVID-19 becomes endemic, understanding antibody response and transfer during pregnancy is crucial to inform policy and vaccination schedules. While good immunogenicity has been shown from SARS-CoV-2 vaccines, few data are available demonstrating functional responses in pregnant populations and infants. METHODS: A prospective, multi-site observational study was completed across 14 centers in England from April 23, 2020, to December 21, 2022. Demographic, COVID infection and vaccination data were collected. Maternal and cord blood samples were taken at delivery, with maternal and neonatal blood samples taken at 6 weeks for participants who had been infected or vaccinated. Antibody concentrations were measured using antibody-dependent complement deposition, antibody-dependent neutrophil phagocytosis, ACE2 inhibition and Roche and EuroImmun antibody binding assays at the UK Health Security Agency. RESULTS: Maternal vaccination and infection both produced an antibody response in 100% of mothers and 93.8% and 92.9% of neonates, respectively, which persisted at 6 weeks in 95%. The strongest response was seen in mothers who were both vaccinated and infected. Anti-spike antibody response decreased almost 25-fold from first to third trimester vaccination (P=0.013). Placental transfer of antibodies post-infection showed varied results depending on the assay used, with higher transfer ratios observed in assays measuring Fc-mediated antibody effector functions and IgG-specific responses. CONCLUSIONS: Maternal vaccination is associated with good immunogenicity and successful antibody transfer to the neonate, particularly with vaccination in early pregnancy. Further study is needed to determine the mechanism by which the timing of vaccination affects antibody transfer. When measuring placental transfer of antibodies, consideration of the assay to use is essential

E003 Shear stress modulates endothelial microparticles shedding

Plasma levels of endothelial microparticles (EMPs) are markers of cardiovascular diseases and contribute to the pathogenesis of atherosclerosis. Laminar shear stress (SS) protects against plaque formation contrarily to oscillatory and low SS. We thus investigated whether different flow patterns (laminar, low or static) could affect EMP release.HUVECs were subjected to high and low SS (15, 1.5 dynes /cm2) or no SS (static) for 24hours. EMPs were isolated from the culture medium and characterized by annexin V labeling using flow cytometry analysis. HUVECs exposed to high SS for 24hours emitted 4 fold less AnnexinV+ EMPs compared to static (p<0.001) and 3 fold less compared to low SS (p<0.01) conditions. This flowdependent EMP shedding was associated with the presence of 1.7 %±0.05, 3.75 %±0.1, 0.4 %±0.06 of TUNEL positive HUVECs in static, low and high conditions, respectively. Treatment of HUVECs with L-NAME (10-4M) significantly increased EMPs in all conditions when compared to untreated cells. Similar EMPs increase was obtained when cells were treated with KT5720, a PKA inhibitor (10-6M) under low and high flow. We further characterized EMPs by determining their surface expression of ICAM-1. ICAM-1 expression on EMPs was significantly increased in low SS and inhibited by high SS when compared to static conditions. Adhesion assays with EMPs-stimulated HUVECs (24hours) increased U937 cells capacity to attach in low SS-EMPs exposed to HUVECs compared to static and high SS EMPs stimulations. This effect was abolished with LFA-pretreated U937 before adhesion suggesting the pro-adhesive properties of low SS-EMPs bearing ICAM-1 at their surface.Altogether, these findings indicate that high SS decreased the thrombotic and adhesive properties of EMPs, which might in part explain their anti-atherogenic effects, whereas low SS induced the shedding of prothrombotic, ICAM-1 positive EMPs, suggesting a novel way by which low SS might affect atherosclerosis

Shear Stress Regulates Angiotensin Type 1 Receptor Expression in Endothelial Cells

Rationale: Shear stress (SS) has an established role in atherosclerotic plaque localization, but how it exerts its protective effect is not fully understood. Objective: To test the hypothesis that SS may downregulate angiotensin type 1 receptors (AT(1)Rs). Angiotensin II has been shown to be proinflammatory and to promote atherosclerosis. Methods and Results: Using immunohistochemistry, we found a pronounced expression of AT(1)R in the inner, atheroprone regions of the aortic arch of C57BL/6 and endothelial NO synthase-deficient (eNOS(-/-)) mice but not eNOS-overexpressing mice. In human umbilical vein endothelial cells (HUVECs), laminar SS (15 dyn/cm(2)) induced a biphasic decrease in AT(1)R protein expression characterized by a first reduction at 1 hour (31+/-4% of static control, P<0.01), partial recovery at 3 hours (65+/-9%), and a second more prolonged decline at 6, 12, and 24 hours (48+/-9%, 36+/-9%, 33+/-5%, respectively, P<0.05). One and 24 hours of SS significantly reduced fluorescent angiotensin binding compared to static HUVECs. Shear-induced downregulation of AT(1)R was abolished by treatment with protein kinase A and G inhibitors or N-G-nitro-L-arginine methyl ester (L-NAME). Fittingly, stimulating static HUVECs with an NO donor decreased AT(1)R protein levels. RT-PCR revealed a significant (P<0.05) decrease of AT(1)R mRNA in HUVECs exposed to SS during 3 (6+/-2% of static control), 6 (4+/-1%), 12 (4+/-1%), and 24 hours (15+/-4%), suggesting a transcriptional downregulation of AT(1)R at length. Finally, angiotensin-induced vascular cell adhesion molecule was abated in HUVECs exposed to SS and in the outer aortic arch of mice. Conclusions: Our results demonstrate that SS may convey some of its atheroprotective effects through downregulation of AT(1)R in endothelial cells. (Circ Res. 2009; 105: 869-875.

Hypoxia Induces Netrin-1 and Unc5b in Atherosclerotic Plaques Mechanism for Macrophage Retention and Survival

Nephrolog

Neuroimmune Guidance Cue Semaphorin 3E Is Expressed in Atherosclerotic Plaques and Regulates Macrophage Retention

Nephrolog