High-Density Lipoprotein Inhibits Serum Amyloid A-Mediated Reactive Oxygen Species Generation and NLRP3 Inflammasome Activation

Serum amyloid A (SAA) is a high-density apolipoprotein whose plasma levels can increase more than 1000-fold during a severe acute-phase inflammatory response and are more modestly elevated in chronic inflammation. SAA is thought to play important roles in innate immunity, but its biological activities have not been completely delineated. We previously reported that SAA deficiency protects mice from developing abdominal aortic aneurysms (AAAs) induced by chronic angiotensin II (AngII) infusion. Here, we report that SAA is required for AngII-induced increases in interleukin-1β (IL-1β), a potent proinflammatory cytokine that is tightly controlled by the Nod-like receptor protein 3 (NLRP3) inflammasome and caspase-1 and has been implicated in both human and mouse AAAs. We determined that purified SAA stimulates IL-1β secretion in murine J774 and bone marrow–derived macrophages through a mechanism that depends on NLRP3 expression and caspase-1 activity, but is independent of P2X7 nucleotide receptor (P2X7R) activation. Inhibiting reactive oxygen species (ROS) by N-acetyl-l-cysteine or mito-TEMPO and inhibiting activation of cathepsin B by CA-074 blocked SAA–mediated inflammasome activation and IL-1β secretion. Moreover, inhibiting cellular potassium efflux with glyburide or increasing extracellular potassium also significantly reduced SAA–mediated IL-1β secretion. Of note, incorporating SAA into high-density lipoprotein (HDL) prior to its use in cell treatments completely abolished its ability to stimulate ROS generation and inflammasome activation. These results provide detailed insights into SAA–mediated IL-1β production and highlight HDL\u27s role in regulating SAA\u27s proinflammatory effects

Role of Serum Amyloid A in Abdominal Aortic Aneurysm and Related Cardiovascular Diseases

Epidemiological data positively correlate plasma serum amyloid A (SAA) levels with cardiovascular disease severity and mortality. Studies by several investigators have indicated a causal role for SAA in the development of atherosclerosis in animal models. Suppression of SAA attenuates the development of angiotensin II (AngII)-induced abdominal aortic aneurysm (AAA) formation in mice. Thus, SAA is not just a marker for cardiovascular disease (CVD) development, but it is a key player. However, to consider SAA as a therapeutic target for these diseases, the pathway leading to its involvement needs to be understood. This review provides a brief description of the pathobiological significance of this enigmatic molecule. The purpose of this review is to summarize the data relevant to its role in the development of CVD, the pitfalls in SAA research, and unanswered questions in the field

The Dual Role of Group V Secretory Phospholipase A\u3csub\u3e2\u3c/sub\u3e in Pancreatic β-Cells

Purpose Group X (GX) and group V (GV) secretory phospholipase A2 (sPLA2) potently release arachidonic acid (AA) from the plasma membrane of intact cells. We previously demonstrated that GX sPLA2 negatively regulates glucose-stimulated insulin secretion (GSIS) by a prostaglandin E2 (PGE2)-dependent mechanism. In this study we investigated whether GV sPLA2 similarly regulates GSIS. Methods GSIS and pancreatic islet-size were assessed in wild-type (WT) and GV sPLA2-knock out (GV KO) mice. GSIS was also assessed ex vivo in isolated islets and in vitro using MIN6 pancreatic beta cell lines with or without GV sPLA2 overexpression or silencing. Results GSIS was significantly decreased in islets isolated from GV KO mice compared to WT mice and in MIN6 cells with siRNA-mediated GV sPLA2 suppression. MIN6 cells overexpressing GV sPLA2 (MIN6-GV) showed a significant increase in GSIS compared to control cells. Though the amount of AA released into the media by MIN6-GV cells was significantly higher, PGE2 production was not enhanced or cAMP content decreased compared to control MIN6 cells. Surprisingly, GV KO mice exhibited a significant increase in plasma insulin levels following i.p. injection of glucose compared to WT mice. This increase in GSIS in GV KO mice was associated with a significant increase in pancreatic islet size and number of proliferating cells in β-islets compared to WT mice. Conclusions Deficiency of GV sPLA2 results in diminished GSIS in isolated pancreatic beta-cells. However, the reduced GSIS in islets lacking GV sPLA2 appears to be compensated by increased islet mass in GV KO mice

Reduction of Oxidative Melt Loss of Aluminum and Its Alloys

This project led to an improved understanding of the mechanisms of dross formation. The microstructural evolution in industrial dross samples was determined. Results suggested that dross that forms in layers with structure and composition determined by the local magnesium concentration alone. This finding is supported by fundamental studies of molten metal surfaces. X-ray photoelectron spectroscopy data revealed that only magnesium segregates to the molten aluminum alloy surface and reacts to form a growing oxide layer. X-ray diffraction techniques that were using to investigate an oxidizing molten aluminum alloy surface confirmed for the first time that magnesium oxide is the initial crystalline phase that forms during metal oxidation. The analytical techniques developed in this project are now available to investigate other molten metal surfaces. Based on the improved understanding of dross initiation, formation and growth, technology was developed to minimize melt loss. The concept is based on covering the molten metal surface with a reusable physical barrier. Tests in a laboratory-scale reverberatory furnace confirmed the results of bench-scale tests. The main highlights of the work done include: A clear understanding of the kinetics of dross formation and the effect of different alloying elements on dross formation was obtained. It was determined that the dross evolves in similar ways regardless of the aluminum alloy being melted and the results showed that amorphous aluminum nitride forms first, followed by amorphous magnesium oxide and crystalline magnesium oxide in all alloys that contain magnesium. Evaluation of the molten aluminum alloy surface during melting and holding indicated that magnesium oxide is the first crystalline phase to form during oxidation of a clean aluminum alloy surface. Based on dross evaluation and melt tests it became clear that the major contributing factor to aluminum alloy dross was in the alloys with Mg content. Mg was identified as the primary factor that accelerates dross formation specifically in the transition from two phases to three phase growth. Limiting magnesium oxidation on the surface of molten aluminum therefore becomes the key to minimizing melt loss, and technology was developed to prevent magnesium oxidation on the aluminum surface. This resulted in a lot of the work being focused on the control of Mg oxidation. Two potential molten metal covering agents that could inhibit dross formation during melting and holding consisting of boric acid and boron nitride were identified. The latter was discounted by industry as it resulted in Boron pick up by the melt beyond that allowed by specifications during plant trials. The understanding of the kinetics of dross formation by the industry partners helped them understand how temperature, alloy chemistry and furnace atmosphere (burner controls--e.g. excess air) effected dross formation. This enables them to introduce in their plant process changes that reduced unnecessary holding at high temperatures, control burner configurations, reduce door openings to avoid ingress of air and optimize charge mixes to ensure rapid melting and avoid excess oxidation

Materials Solutions for Hydrogen Delivery in Pipelines

The main objective of the study is as follows: Identify steel compositions/microstructures suitable for construction of new pipeline infrastructure and evaluate the potential use of the existing steel pipeline infrastructure in high pressure gaseous hydrogen applications. The microstructures of four pipeline steels were characterized and tensile testing was conducted in gaseous hydrogen and helium at pressures of 5.5 MPa (800 psi), 11 MPa (1600 psi) and 20.7 MPa (3000 psi). Based on reduction of area, two of the four steels that performed the best across the pressure range were selected for evaluation of fracture and fatigue performance in gaseous hydrogen at 5.5 MPa (800 psi) and 20.7 MPa (3000 psi). The basic format for this phase of the study is as follows: Microstructural characterization of volume fraction of phases in each alloy; Tensile testing of all four alloys in He and H{sub 2} at 5.5 MPa (800 psi), 11 MPa (1600 psi), and 20.7 MPa (3000 psi). RA performance was used to choose the two best performers for further mechanical property evaluation; Fracture testing (ASTM E1820) of two best tensile test performers in H{sub 2} at 5.5 MPa (800 psi) and 20.7 MPa (3000 psi); Fatigue testing (ASTM E647) of two best tensile test performers in H2 at 5.5 MPa (800 psi) and 20.7 MPa (3000 psi) with frequency =1.0 Hz and R-ratio=0.5 and 0.1

Serum amyloid A and inflammasome activation : a link to breast cancer progression?

CITATION: Fourie, C. et al. 2021.Serum amyloid A and inflammasome activation: A link to breast cancer progression? Cytokine & Growth Factor Reviews, 59:62-70. doi:10.1016/j.cytogfr.2020.10.006The original publication is available at https://www.sciencedirect.com/journal/cytokine-and-growth-factor-reviewsBreast cancer is the most frequently diagnosed cancer in women globally. Although there have been many significant advances made in the diagnosis and treatment of breast cancer, numerous unresolved challenges remain, which include prevention, early diagnosis, metastasis and recurrence. The role of inflammation in cancer development is well established and is believed to be one of the leading hallmarks of cancer progression. Recently, the role of the inflammasome, a cytosolic multiprotein complex, has received attention in different cancers. By contributing to the activation of inflammatory cytokines the inflammasome intensifies the inflammatory cascade. The inflammasome can be activated through several pathways, which include the binding of pattern associated molecular patterns (PAMPs) and damage associated molecular patterns (DAMPs) to toll-like receptors (TLRs). Serum amyloid A (SAA), a non-specific acute-phase protein, can function as an endogenous DAMP by binding to pattern recognition receptors like TLRs on both breast cancer cells and cancer associated fibroblasts (CAFs). SAA can thus stimulate the production of IL-1β, thereby creating a favourable inflammatory environment to support tumour growth. The aim of this review is to highlight the possible role of SAA as an endogenous DAMP in the tumour microenvironment (TME) thereby promoting breast cancer growth through the activation of the NLRP3 inflammasome.https://www.sciencedirect.com/science/article/pii/S1359610120302203?via%3DihubPublishers versio

Visualización en tres dimensiones, los mapas de amenaza volcánica educan al ciudadano común

Even the most reliable volcanic hazard map will be of little use, unless it is presented in terms that are useful to politics, emergency management officials and citizens. The Volcanic Hazard Map of the Nevado del Ruiz Volcano (Colombia), was superimposed on Landsat TM 5 data and digital elevation models, in order to generate perspective views for making the volcanic hazard situations comprehensible to the common people.This 3-D visualization methodology could be used with any volcanic hazard map available. The products generated help to improve the communication between volcanologists and people not familiar with volcanoes, in order to avoid confusion, misunderstanding and strained relations between scientists and persons responsible for the public welfare, during any volcanic emergency crisis.Hasta el mapa de amenaza volcánica más confiable, será de poca utilidad si es presentado de una forma que no lo haga útil para políticos, oficiales que manejan situaciones de emergencia y ciudadanos comunes. Se realizó la superposición del Mapa de Amenaza Volcánica del Volcán Nevado del Ruiz (Colombia), sobre imágenes Landsat TM y modelos digitales de elevación, para generar vistas en perspectiva que hagan comprensibles para el público en general, las situaciones de amenaza volcánica.Esta metodología de visualización en tres dimensiones, podría utilizarse en cualquier mapa de amenaza volcánica disponible. Los productos generados ayudan a mejorar la comunicación entre vulcanólogos y gente no familiarizada con los volcanes, para evitar confusiones, malos entendidos y malas relaciones entre científicos y personas a cargo de la seguridad pública, durante cualquier crisis de emergencia volcánica. &nbsp

Serum Amyloid A3 is a High Density Lipoprotein-Associated Acute-Phase Protein

Serum amyloid A (SAA) is a family of acute-phase reactants. Plasma levels of human SAA1/SAA2 (mouse SAA1.1/2.1) can increase ≥ 1,000-fold during an acute-phase response. Mice, but not humans, express a third relatively understudied SAA isoform, SAA3. We investigated whether mouse SAA3 is an HDL-associated acute-phase SAA. Quantitative RT-PCR with isoform-specific primers indicated that SAA3 and SAA1.1/2.1 are induced similarly in livers (∼2,500-fold vs. ∼6,000-fold, respectively) and fat (∼400-fold vs. ∼100-fold, respectively) of lipopolysaccharide (LPS)-injected mice. In situ hybridization demonstrated that all three SAAs are produced by hepatocytes. All three SAA isoforms were detected in plasma of LPS-injected mice, although SAA3 levels were ∼20% of SAA1.1/2.1 levels. Fast protein LC analyses indicated that virtually all of SAA1.1/2.1 eluted with HDL, whereas ∼15% of SAA3 was lipid poor/free. After density gradient ultracentrifugation, isoelectric focusing demonstrated that ∼100% of plasma SAA1.1 was recovered in HDL compared with only ∼50% of SAA2.1 and ∼10% of SAA3. Thus, SAA3 appears to be more loosely associated with HDL, resulting in lipid-poor/free SAA3. We conclude that SAA3 is a major hepatic acute-phase SAA in mice that may produce systemic effects during inflammation

An unconventional diacylglycerol kinase that regulates phospholipid synthesis and nuclear membrane growth

Changes in nuclear size and shape during the cell cycle or during development require coordinated nuclear membrane remodeling, but the underlying molecular events are largely unknown. We have shown previously that the activity of the conserved phosphatidate phosphatase Pah1p/Smp2p regulates nuclear structure in yeast by controlling phospholipid synthesis and membrane biogenesis at the nuclear envelope. Two screens for novel regulators of phosphatidate led to the identification of DGK1. We show that Dgk1p is a unique diacylglycerol kinase that uses CTP, instead of ATP, to generate phosphatidate. DGK1 counteracts the activity of PAH1 at the nuclear envelope by controlling phosphatidate levels. Overexpression of DGK1 causes the appearance of phosphatidate-enriched membranes around the nucleus and leads to its expansion, without proliferating the cortical endoplasmic reticulum membrane. Mutations that decrease phosphatidate levels decrease nuclear membrane growth in pah1Δ cells. We propose that phosphatidate metabolism is a critical factor determining nuclear structure by regulating nuclear membrane biogenesis

Integrated Lipidomics in the Secreted Phospholipase A2 Biology

Mammalian genomes encode genes for more than 30 phospholipase A2s (PLA2s) or related enzymes, which are subdivided into several subgroups based on their structures, catalytic mechanisms, localizations and evolutionary relationships. More than one third of the PLA2 enzymes belong to the secreted PLA2 (sPLA2) family, which consists of low-molecular-weight, Ca2+-requiring extracellular enzymes, with a His-Asp catalytic dyad. Individual sPLA2 isoforms exhibit unique tissue and cellular localizations and enzymatic properties, suggesting their distinct pathophysiological roles. Recent studies using transgenic and knockout mice for several sPLA2 isoforms, in combination with lipidomics approaches, have revealed their distinct contributions to various biological events. Herein, we will describe several examples of sPLA2-mediated phospholipid metabolism in vivo, as revealed by integrated analysis of sPLA2 transgenic/knockout mice and lipid mass spectrometry. Knowledge obtained from this approach greatly contributes to expanding our understanding of the sPLA2 biology and pathophysiology