Atherosclerosis is an inflammatory disease. Because high plasma concentrations of cholesterol, in particular those of low-density lipoprotein (LDL) cholesterol, are one of the principal risk factors for atherosclerosis,1 the process of atherogenesis has been considered by many to consist largely of the accumulation of lipids within the artery wall; however, it is much more than that. Despite changes in lifestyle and the use of new pharmacologic approaches to lower plasma cholesterol concentrations,2,3 cardiovascular disease continues to be the principal cause of death in the United States, Europe, and much of Asia.4,5 In fact, the lesions of atherosclerosis represent . . .

https://www.nejm.org/doi/pdf/10.1056/NEJM199901143400207

Atherosclerosis — An Inflammatory Disease

Atherosclerosis is an Inflammatory Disease

Apoptosis is a cell suicide mechanism that enables metazoans to control cell number in tissues and to eliminate individual cells that threaten the animal's survival. Certain cells have unique sensors, termed death receptors, on their surface. Death receptors detect the presence of extracellular death signals and, in response, they rapidly ignite the cell's intrinsic apoptosis machinery.

/pdf/death-receptors-signaling-and-modulation-yjd5e96rtz.pdf

Death receptors: signaling and modulation

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(05)71142-9.pdf

Acquired mutation of the tyrosine kinase JAK2 in human myeloproliferative disorders.

Two different tumour-necrosis factors (TNFs), first isolated in 1984, were found to be cytotoxic to tumour cells and to induce tumour regression in mice. Research during the past two decades has shown the existence of a superfamily of TNF proteins consisting of 19 members that signal through 29 receptors. These ligands, while regulating normal functions such as immune responses, haematopoiesis and morphogenesis, have also been implicated in tumorigenesis, transplant rejection, septic shock, viral replication, bone resorption, rheumatoid arthritis and diabetes; so indicating their role as 'double-edged swords'. These cytokines either induce cellular proliferation, survival, differentiation or apoptosis. Blockers of TNF have been approved for human use in treating TNF-linked autoimmune diseases in the United States and other countries.

/pdf/signalling-pathways-of-the-tnf-superfamily-a-double-edged-aixlu7oo9e.pdf

Signalling pathways of the TNF superfamily: a double-edged sword.

Mammalian cells proteolytically release (shed) the extracellular domains of many cell-surface proteins. Modification of the cell surface in this way can alter the cell's responsiveness to its environment and release potent soluble regulatory factors. The release of soluble tumour-necrosis factor-alpha (TNF-alpha) from its membrane-bound precursor is one of the most intensively studied shedding events because this inflammatory cytokine is so physiologically important. The inhibition of TNF-alpha release (and many other shedding phenomena) by hydroxamic acid-based inhibitors indicates that one or more metalloproteinases is involved. We have now purified and cloned a metalloproteinase that specifically cleaves precursor TNF-alpha. Inactivation of the gene in mouse cells caused a marked decrease in soluble TNF-alpha production. This enzyme (called the TNF-alpha-converting enzyme, or TACE) is a new member of the family of mammalian adamalysins (or ADAMs), for which no physiological catalytic function has previously been identified. Our results should facilitate the development of therapeutically useful inhibitors of TNF-alpha release, and they indicate that an important function of adamalysins may be to shed cell-surface proteins.

A metalloproteinase disintegrin that releases tumour-necrosis factor-α from cells

TRAIL is a member of the tumor necrosis factor (TNF) family of cytokines and induces apoptosis in a wide variety of cells. Based on homology searching of a private database, a receptor for TRAIL (DR4 or TRAIL-R1) was recently identified. Here we report the identification of a distinct receptor for TRAIL, TRAIL-R2, by ligand-based affinity purification and subsequent molecular cloning. TRAIL-R2 was purified independently as the only receptor for TRAIL detectable on the surface of two different human cell lines that undergo apoptosis upon stimulation with TRAIL. TRAIL-R2 contains two extracellular cysteine-rich repeats, typical for TNF receptor (TNFR) family members, and a cytoplasmic death domain. TRAIL binds to recombinant cell-surface-expressed TRAIL-R2, and TRAIL-induced apoptosis is inhibited by a TRAIL-R2-Fc fusion protein. TRAIL-R2 mRNA is widely expressed and the gene encoding TRAIL-R2 is located on human chromosome 8p22-21. Like TRAIL-R1, TRAIL-R2 engages a caspase-dependent apoptotic pathway but, in contrast to TRAIL-R1, TRAIL-R2 mediates apoptosis via the intracellular adaptor molecule FADD/MORT1. The existence of two distinct receptors for the same ligand suggests an unexpected complexity to TRAIL biology, reminiscent of dual receptors for TNF, the canonical member of this family.

Trail-r2: a novel apoptosis-mediating receptor for trail

In eukaryotic cells, protein disulfide isomerase (PDI) found in the endoplasmic reticulum (ER) catalyzes disulfide bond exchange and assists in protein folding of newly synthesized proteins. PDI also functions as a molecular chaperone and has been found associated with proteins in the ER. In addition, PDI functions as a subunit of two more complex enzyme systems: the prolyl-4-hydroxylase and the triacylglycerol transfer proteins. Increasing PDI activity in bacterial, yeast, and insect cell expression systems can lead to increased secretion of heterologous proteins containing disulfide bridges. Since Chinese hamster ovary (CHO) cells are widely used for the expression of recombinant proteins, we expressed recombinant human PDI (rhu PDI) in CHO cells to increase cellular PDI levels and examined its effect on the secretion of two different recombinant proteins: interleukin 15 (IL-15) and a tumor necrosis factor receptor:Fc fusion protein (TNFR:Fc). Secretion of TNFR:Fc (a disulfide-rich protein) is decreased in cells overexpressing PDI; the TNFR:Fc protein is retained inside these cells and colocalizes with the overexpressed rhu PDI protein in the endoplasmic reticulum. PDI overexpression did not result in intracellular retention of IL15. The nature of the interaction between PDI and TNFR:Fc was further investigated by expressing a disulfide isomerase mutant PDI in CHO cells to determine if the functional activity of PDI is involved in the cellular retention of TNFR:Fc protein.

Kenneth A. Schooley

Papers

A metalloproteinase disintegrin that releases tumour-necrosis factor-α from cells

Trail-r2: a novel apoptosis-mediating receptor for trail

Effect of PDI overexpression on recombinant protein secretion in CHO cells.

Identification of a distinct low-affinity receptor for human interleukin-4 on pre-B cells

Fas Ligand Mediates Activation-induced Cell Death in Human T Lymphocytes By Mark g. Alderson, Teresa W. Tough, Terri Davis-Smith,