Stimulation of Akt poly-ubiquitination and proteasomal degradation in P388D1 cells by 7-ketocholesterol and 25-hydroxycholesterol.

Akt plays a role in protecting macrophages from apoptosis induced by some oxysterols. Previously we observed enhanced degradation of Akt in P388D1 moncocyte/macrophages following treatment with 25-hydroxycholesterol (25-OH) or 7-ketocholesterol (7-KC). In the present report we examine the role of the ubiquitin proteasomal pathway in this process.

Involvement of xeroderma pigmentosum group A (XPA) in progeria arising from defective maturation of prelamin A.

Cellular accumulation of DNA damage has been widely implicated in cellular senescence, aging, and premature aging. In Hutchinson-Gilford progeria syndrome (HGPS) and restrictive dermopathy (RD), premature aging is linked to accumulation of DNA double-strand breaks (DSBs), which results in genome instability. However, how DSBs accumulate in cells despite the presence of intact DNA repair proteins remains unknown.

Alterations in mitosis and cell cycle progression caused by a mutant lamin A known to accelerate human aging.

Mutations in the gene encoding nuclear lamin A (LA) cause the premature aging disease Hutchinson-Gilford Progeria Syndrome. The most common of these mutations results in the expression of a mutant LA, with a 50-aa deletion within its C terminus. In this study, we demonstrate that this deletion leads to a stable farnesylation and carboxymethylation of the mutant LA (LADelta50/progerin).

DNA damage responses in progeroid syndromes arise from defective maturation of prelamin A.

The genetic diseases Hutchinson-Gilford progeria syndrome (HGPS) and restrictive dermopathy (RD) arise from accumulation of farnesylated prelamin A because of defects in the lamin A maturation pathway. Both of these diseases exhibit symptoms that can be viewed as accelerated aging. The mechanism by which accumulation of farnesylated prelamin A leads to these accelerated aging phenotypes is not understood.

Farnesylated lamins, progeroid syndromes and farnesyl transferase inhibitors.

Three mammalian nuclear lamin proteins, lamin B(1), lamin B(2) and the lamin A precursor, prelamin A, undergo canonical farnesylation and processing at CAAX motifs. In the case of prelamin A, there is an additional farnesylation-dependent endoproteolysis, which is defective in two congenital diseases: Hutchinson-Gilford progeria (HGPS) and restrictive dermopathy (RD). These two diseases arise respectively from defects in the prelamin A substrate and the enzyme (ZmpSte24) that processes it.

Acyl-coenzyme A:cholesterol acyltransferase promotes oxidized LDL/oxysterol-induced apoptosis in macrophages.

7-Ketocholesterol (7KC) is a cytotoxic component of oxidized low density lipoproteins (OxLDLs) and induces apoptosis in macrophages by a mechanism involving the activation of cytosolic phospholipase A2 (cPLA2). In the current study, we examined the role of ACAT in 7KC-induced and OxLDL-induced apoptosis in murine macrophages. An ACAT inhibitor, Sandoz 58-035, suppressed 7KC-induced apoptosis in P388D1 cells and both 7KC-induced and OxLDL-induced apoptosis in mouse peritoneal macrophages (MPMs).

Reduced macrophage apoptosis is associated with accelerated atherosclerosis in low-density lipoprotein receptor-null mice.

Objective: The majority of apoptotic cells in atherosclerotic lesions are macrophages. However, the pathogenic role of macrophage apoptosis in the development of atherosclerosis remains unclear. Elevated expression of Bax, one of the pivotal proapoptotic proteins of the Bcl-2 family, has been found in human atherosclerotic plaques.

Prelamin A endoproteolytic processing in vitro by recombinant Zmpste24.

The nuclear lamins form a karyoskeleton providing structural rigidity to the nucleus. One member of the lamin family, lamin A, is first synthesized as a 74 kDa precursor, prelamin A. After the endopeptidase and methylation reactions which occur after farnesylation of the CAAX-box cysteine, there is a second endoproteolysis that occurs 15 amino acids upstream from the C-terminal farnesylated cysteine residue.

AKT/protein kinase B regulation of BCL family members during oxysterol-induced apoptosis.

Cells of the vasculature, including macrophages, smooth muscle cells, and endothelial cells, exhibit apoptosis in culture upon treatment with oxidized low density lipoprotein, as do vascular cells of atherosclerotic plaque. Several lines of evidence support the hypothesis that the apoptotic component of oxidized low density lipoprotein is one or more oxysterols, which have been shown to induce apoptosis through the mitochondrial pathway. Activation of the mitochondrial pathway of apoptosis is regulated by members of the BCL family of proteins.

Acellular dermal matrix allograft in the treatment of mucogingival defects in children: illustrative case report.

Mucogingival defects can occur in children and are of particular concern when orthodontic treatment is indicated. The rationale for surgical intervention is predicated on the need to repair the mucogingival defect and to establish adequate thickness of attached gingiva. The free gingival graft, usually obtained from the hard palate, is often used to increase the amount of attached gingiva.

Arachidonate metabolism and the signaling pathway of induction of apoptosis by oxidized LDL/oxysterol.

Owing at least in part to oxysterol components that can induce apoptosis, oxidized LDL (oxLDL) is cytotoxic to mammalian cells with receptors that can internalize it. Vascular cells possess such receptors, and it appears that the apoptotic response of vascular cells to the oxysterols borne by oxLDL is an important part of the atherogenic effects of oxLDL. Thus, an analysis of the signaling pathway of apoptotic induction by oxysterols is of value in understanding the development of atherosclerotic plaque.

Mechanisms of oxysterol-induced apoptosis.

The rationale for the present review is that oxysterols found in oxidized LDL (oxLDL) play a role in atherogenesis. This perspective is based on studies that show that induction of apoptosis in vascular cells is an important process in atherogenesis, that apoptosis can be induced by oxLDL, and that the oxysterol component of oxLDL is responsible for its proapoptotic activity. The evidence for these concepts is reviewed, as are studies on the mechanisms by which oxysterols can induce apoptosis.

Indirect cytotoxicity of dental materials: a study with Transwell inserts and the neutral red uptake assay.

A modification of the Transwell insert methodology was evaluated by using the neutral red uptake (NRU) assay in a cytotoxicity test. The Transwell insert methodology was developed to assess the biocompatibility of solid materials used in dentistry and, when initially designed, used the release of radiochromium ((51)Cr) in the cytotoxicity assay. Another aim of this study was to evaluate different exposure regimes with which to assess cytotoxicity.

Concepts in Ras-directed therapy.

Ras proteins are key transducers of growth signals regulated by cell surface receptors. They are anchored to the inner surface of the cell membrane where receptor-mediated signalling induces Ras activation (GDP/GTP exchange) and inactivation (stimulation of Ras GTPase activity). Ras-GTP in turn activates a multitude of signalling cascades controlling cell growth and differentiation.

Functional aspects of polyisoprenoid protein substituents: roles in protein-protein interaction and trafficking.

There are now numerous examples of post-translational modification with geranylgeranyl or farnesyl substituents. Once thought of as solely a mechanism for association of proteins with membranes, other functional aspects of protein prenylation have come to be appreciated. Although, in almost all instances, such proteins are membrane associated, they are often found to also engage in protein-protein interactions.

25-Hydroxycholesterol activates a cytochrome c release-mediated caspase cascade.

We have previously shown that 25-hydroxycholesterol (25-OHC) treated CHO-K1 cells could be used as a model to investigate the signaling pathway of apoptosis induced by oxidized LDL in vascular cells. In the present study, we examine the execution phase of the apoptotic pathway in CHO-K1 cell death induced by 25-OHC. Oxysterol-induced apoptosis in CHO-K1 was accompanied by caspase activation and was preceded by mitochondrial cytochrome c release.

Transcriptional homeostatic control of membrane lipid composition.

Plasma membranes have a structural property, commonly referred to as membrane fluidity, that is compositionally regulated. The two main features of plasma membrane lipid composition that determine membrane fluidity are the ratio of cholesterol to phospholipids and the ratio of saturated to unsaturated fatty acids that are incorporated into the phospholipids. These ratios are determined, at least in part, by regulation of membrane lipid biosynthesis-particularly that of cholesterol and oleate.

Recent advances in the study of prenylated proteins.

Post-translational modification of proteins with isoprenoids was first recognized as a general phenomenon in 1984. In recent years, our understanding, including mechanistic studies, of the enzymatic reactions associated with these modifications and their physiological functions has increased dramatically. Of particular functional interest is the role of prenylation in facilitating protein-protein interactions and membrane-associated protein trafficking.

Isolation of a somatic cell mutant resistant to the induction of apoptosis by oxidized low density lipoprotein.

Oxidized low density lipoprotein (oxLDL) induces apoptosis in macrophages, smooth muscle cells, and endothelial cells. To elucidate the molecular mechanism of oxLDL-induced cytotoxicity and determine its tissue specificity, we have used Chinese hamster ovary (CHO)-K1 cells expressing human CD36 (CHO/CD36). Expression of CD36 rendered these cells susceptible to killing by oxLDL.

The versatility of calcium sulfate: resolving periodontal challenges.

The multifaceted properties of calcium sulfate demonstrate its usefulness in periodontal practice. Calcium sulfate can function as a resorbable space filler, a resorbable barrier (compatible with guided tissue regeneration principles) and as a vehicle for controlled-release chemotherapy. Various periodontal challenges are demonstrated through case reports using calcium sulfate.

Subcellular localization and partial purification of prelamin A endoprotease: an enzyme which catalyzes the conversion of farnesylated prelamin A to mature lamin A.

The nuclear lamina protein, lamin A is produced by proteolytic cleavage of a 74 kDa precursor protein, prelamin A. The conversion of this precursor to mature lamin A is mediated by a specific endoprotease, prelamin A endoprotease. Subnuclear fractionation indicates that the prelamin A endoprotease is localized at the nuclear membrane.

Oleate potentiates oxysterol inhibition of transcription from sterol regulatory element-1-regulated promoters and maturation of sterol regulatory element-binding proteins.

Activation of genes containing SRE-1 (sterol regulatory element 1) sequences is known to be under the regulation of sterols through modulation of the proteolytic maturation of SREBPs (SRE-1-binding proteins). Previous work has demonstrated SREBP-mediated transcriptional activation of genes encoding enzymes of sterol and fatty acid biosynthesis. Because synthesis of both sterols and C18 fatty acids are required for cell growth, in the absence of exogenous supplements of these lipids, we examined the hypothesis that fatty acid can also be regulatory in SREBP maturation.

Triclosan: cytotoxicity, mode of action, and induction of apoptosis in human gingival cells in vitro.

The in vitro cytotoxicology of triclosan, the active ingredient in some mouthrinses and dentifrices used in the prevention and treatment of gingivitis and plaque, was studied using the Smulow-Glickman (S-G) human gingival epithelial cell line. The 24 h midpoint cytotoxicity value was 0.05-0.

Evidence for a high affinity, saturable, prenylation-dependent p21Ha-ras binding site in plasma membranes.

Oncogenic p21ras proteins can only exert their stimulation of cellular proliferation when plasma membrane-associated. This membrane association has an absolute requirement for post-translational modification with isoprenoids. The mechanism by which isoprenoids participate in the specific association of p21ras with plasma membranes is the subject of this report.